This guide is to provide a rather rough guideline on how to build Windrunner with supporting and ganking in mind, so preferably a side-lane. Windrunner can work as a somewhat decent semi-carry, but if you're looking to fill that role, you should choose a hero better suited for it.
This is in no way the be-all end-all guide on how to play her, as many items and skill builds should be used depending on the situation, you should always attempt to pick an item or skill that will help you at the moment in time, I cannot emphasize this enough.
Some things to keep in mind while reading this guide and playing DotA in general.
I will give a rough explanation on how her skills should be used, if you want to know the exact specifics on what each skill does, please turn to the tooltip.
This is what most would describe as Windrunner's bread and butter skill, it's one of the most powerful crowd control spells in the game, with the ability to shackle 2 heroes together for 3.75 seconds or a single hero for .75 seconds. This skill is best used when 2 enemy heroes are lined up, or an enemy hero is lined up with a tree or enemy creep; that said, do not be afraid to use the skill when there's nothing to latch it onto, as the 'mini-stun' portion of the skill can still slow a fleeing or chasing enemy down or prevent them from channeling or teleporting.
This spell can shackle two enemies together, stunning them both.
Trees created by Nature's Prophet's Sprout spell are valid targets for shackling.
Can shackle the target to an enemy or tree up to 525/500 units behind it.
Windrunner's Power-Shot is a great long-range nuke that can be used in numerous situations; common ways to use the spell are for long-range harassment or last-hitting. Try to not use your level 1 Powershot unless necessary, as it's damage:mana ratio isn't that greet early on. You can pick-off or 'snipe' low-health heroes from great range as well as use it to destroy trees to escape or chase. The shot can be channeled for up to 1 second, increasing in damage the longer it's channeled, because of this you should attempt to lead your shot somewhat to predict where the target will be after the channel and attempt to hit the hero while colliding with as few enemy creeps/heroes as possible, to maximize the shot's damage. The shot retains the tree clearing effect regardless of how long it's charged, so prepare to cancel the channel as soon as possible when escaping.
Damage type: Magical
The arrow initially moves at a rate of 3000 units per second.
The arrow is slowed a little each time it hits an enemy or a tree.
This spell destroys trees.
This ability has a short channeling time. If canceled before Lyralei finishes channeling, the arrow will deal less damage.
A great escape spell, giving Windrunner multiple effects that will help her get out of many a dire situation when used properly. The spell will allow Windrunner to slow enemy heroes and creeps that she passes near, as well as granting a significant speed boost and 100% evasion for 5 seconds when maxed out. Though the spell is defensive in nature, it can be used to catch up to and slow enemy heroes. The evasion effect of the spell is commonly overlooked, it can be used in a fight you're committed to, as you can still attack and cast spells while retaining the buff, which will more often than not catch enemies off guard and will throw them into disarray as you continue to fight and take no physical damage.
The slow will affect enemies with magic immunity.
Projectiles that began tracking Windrunner before this ability was activated will not be evaded.
Focus Fire (R):
A rather lackluster ultimate for the standard Windrunner, this spell is mainly useful for structures or on a stationary/commited hero after using all of your items/abilities on them, but even then, it remains being a so-so alternative to auto-attacks and moving. I generally get it at 14, 15, 16, but if you see it being useful for you before then, feel free to grab it earlier. Though the skill can be enhanced with Aghanim's Scepter, giving it a reduced cooldown and removing the penalty on attack modifiers ('Orbs') effects and items, this doesn't warrant it's rather hefty price and no utility, she has other much more needed items, though if you were attempting a carry Windrunner, it's a decent item.
The damage reduction affects all damage from Lyralei while the spell is active, including alternate damage such as unique attack modifiers.
Can target buildings and magic immune units.
Depending on whether your team has other supports will affect what items you begin with, the most important thing your team should have is a Animal Courier, followed by Observer Ward and upgrading the courier to a Flying Courier. Do not buy more than 1 of these at the beginning of the game unless you think you can handle it, as you will be hindering yourself a bit too much. You should then buy 3 Iron Branch to help with damage, health and mana, which will in most games lead up to building a Magic Wand. Lastly, you should buy regen, what you choose to buy is largely up to you, I am more partial to Tangos over Healing Salves, but you can decide if you'd like to get either, 2 of one, or 1 of each. You can also buy clarity's, but I don't find myself spamming too many spells early game to make it necessary.
You should attempt to get Boots of Speed or Observer Ward first, depending on the lane and whether or not your team already has wards down. Best case scenario you would like to like to carry a Town Portal Scroll on you at all times after level 3 throughout the rest of the game, but depending on how well the lane is going you may need to purchase more regen to stay in lane. If your team has yet to have a Flying Courier and it's being used frequently, you may want to upgrade it to flying at some point. Eventually try to upgrade your Boots of Speed into Phase Boots, which will provide you with more damage and another speed increase and unit walking ability.
As the game progresses and the laning phase begins to end, you'd like to keep your team's vision up with warding while still holding onto a teleport scroll at all times. Your next item to build is Force Staff, a versatile item that can be used with great effect for offense and defense.
During mid-game you'd like to get a Mekansm if no one on your team has begun to build one already, if they have, you can build another, but generally you'd like to have only 1 on your team, so a good alternative would be Pipe of Insight, if they have a good amount of magic damage on the enemy team. If they don't have much magic damage, Eul's Scepter of Divinity is another versatile item that can be used to save a teammate being focused, interrupt an enemy channeling/chasing a teammate or dodge an ability used by an enemy.
Late-game just about every intellect or spell-caster hero aims for a Scythe of Vyse, one of the best utility items in the game, generally you should attempt to use the item's effect on a hero with high dps or great team-fight skills, as always, use your discretion on whom you should use this on.
Usually you'd like to complete the standard build before buying anything I've listed in this section, but if their magic damage and effects are just too much of a problem, Black-King Bar is the go-to item, though generally you'd like to finish at least 1 of your support items before building it. If you need a little more health and a reliable invisibility reveal, Necronomicon is a great item as it not only provides both of those, but as well as a granting 2 minions; one with a move-speed aura and the other with a mana-drain nuke.
If you're content with your health, but are facing a lot of physical damage, Shiva's Guard provides a good amount of armor, as well as an attack speed slow aura and a move speed slow active in an aoe around you. Boots of Travel can replace your phase boots in the end-game, removing the necessity of carrying a tp scroll, and allowing you to tp to friendly creeps. If you find yourself wanting more hp, Bloodstone is the way to go, providing you with survivability and an aoe heal to your team on death. If you have a decent amount of health and are finding yourself facing heroes with a lot of burst and/or you're getting focused, Blade Mail is a good item on virtually any hero, providing a damage-reflection ability.
Leave Base after buying a courier, wards or flying upgrade. Try to buy only one. Buy 3x Branches and 1-2x Tango or Salves. I generally skill Windrun first, to give you an escape if the enemy team tries to first blood you, or you find yourself out of position early.
Head to your lane (preferably a side lane), after setting your Observer Ward(s) if you have them. If you're laning with a carry or a hero that needs creep kills, try to harass the enemy back to give your partner breathing room so he can last hit and deny the enemy's last hits. If paired with a another crowd-controller/nuker, you can try to kill at level 3-4+, work on buying your Phase Boots while keeping wards up and upgrading your courier if need be.
You can do well with a bit of farm, but if your lane partner doesn't need your help in lane and you see open opportunity in the other lanes, feel free to carry some tp scrolls and roam and gank, making sure to call out to your teammates if you decide to do so, you should be getting most of your farm via ganking, so you can finish your Force Staff.
As the game progresses your window for ganking will begin to close, as the enemy team will begin to stay together and your team will have to do the same, so try to take advantage of it while you can.
In team fights, try and stay back as you're pretty fragile, remembering to use not only your skills, but all of your activatable items. If you don't use your ultimate in a team fight, always remember to use it on towers as it can tear through them pretty fast.
Always remember to keep a tp on you, keep wards up and remembering the ways to use your items and abilities as they can provide a great amount of utility.
Team work as any support hero begins before you even leave the base, you want to provide your team with an Animal Courier or Observer Wards, I've said this numerous times in the guide because it's that important. Try and place wards as soon as they go down to keep as close to 100% uptime as possible, this is hard to maintain but do your best and your time will be thankful.
Positioning is key for all heroes in DotA, especially when preparing for a team fight, with Windrunner, you want to try and stay on the outside of the fight because of your low health and keeping your eye out for clumped enemies for using Powershot and Shackleshot as well as your support items such as Mekansm, Pipe of Insight, Eul's Scepter of Divinity etc.
I hope I've provided you with an idea of what your role should be in the game when playing Windrunner and what viable options you have in terms of building items. Like most heroes, it may take a few games to get the 'feel' for her abilities and animations, but I'm sure you'll be satisfied with the utility she brings to the team.
I realize this guide isn't exactly concise, I attribute this to being 1 AM and my first guide, so if you have any suggestions to improve this guide's formatting or information please feel free to comment.