This is a guide to Tinker. I'll try to give a simple guide based on how I learned to play tinker by experience and by watching other players such as Playmate and EG.Misery(for pubs ofcourse). I never made a guide before, nor have I been on this site for long so forgive me if my guide lacks polish. Also, I'm admittingly not a dota veteran, so forgive me if my jargon is off as I come from a different genre of competitive games.
Tinker is a Hero very dependent on his nukes and spells for damage and farming. Tinker is a very squishy hero, and must depend on his items in order to avoid damage since he lacks any natural escape. He also is a very mana hungry character and his spells not only have a high cost, but long cooldowns without rearm. He requires both good map awareness to better utilize boots of travel, as well as have good micro for the plethora of active ability items he can use as well as trying to avoid CC and nukes with his good foot speed or items.
Cause why not?
+Very powerful ganker early game, with powerful and long range nukes
+Can make the most out of active ability items
+Fast and super mobile with BoT
+Great pusher and farmer mid game
+Great counter pusher/defender
-Extremely mana hungry
-Very dependent on BoT
-CC/Silence kills you
When it comes to items, tinker is rather straightforward. Boots, boots, boots. Get those boots of travel, they are extremely important to tinker, pretty much a necessity. Your goal is too always get boots by mid game at the latest. I'll explain why below.
I know the game recommends this, but valve is just trolling new tinker players. Why not? Firstly, it is not affected by rearm, and it takes the slots of other items that tinker can make the most out of. Secondly, your not some auto attack carry or in your face strength hero. Your damage comes in bursts and from a range. BKB isn't worth it because you don't deal a lot of damage in a short amount of time in range of CC which BKB is good for. You shouldn't be rearming in the middle of a big teamfight, and if you were to use BKB for that purpose, it would only help you for so many rearms. There are better anti-cc items for tinker's playstyle. Lastly, the stats aren't good at all for tinker for the price. Don't get this.
Sometimes I see blink, but it provides no stats, cannot be used if you get hit even by an auto attack for three seconds, and you already have plenty of mobility with BoT that you don't need to be blinking everywhere. Personally I don't see this as a worthy investment on tinker. Force staff can affect teammates as well as enemies, gives better stats, costs less mana per use, and is not put on cooldown by attacks. Oh, and they cost nearly the same. I think as far as saving yourself from ganks and tinker killers, force staff is better. Leave blink for the initiators.
I have seen many tinkers get this before boots of Travel or shortly after, and I would heavily advise against this. Firstly, and item that costs this much should never come before boots, which opens up your farming potential. Secondly, i'd have to say that the Soul Ring is a MUCH cheaper and more effective mana sustain, with an active that works well with rearm and gives tinker burst mana regen which I feel he needs often. You'll also have bottle and a tp back to base. The HP regen isn't needed on tinker because again, the idea with playing tinker is to not get hit. Any HP regen needed should be taken care of by TP'ing back to base or using a bottle. If you do get hit with tinker, no amount of HP regen will save you anyway.
All of tinker's abilities are good in one way or another. They also costs a ****ton of mana, so they aren't spammable, and doing so will leave you with nothing. Make sure to use tinker's spells when they count, even when you have boots. Personally, I feel tinker's skill point timings are based of when you get certain items, rather than a set in stone order. Still, his first two skills should always be maxed out first.
Fisrt and formost, max out laser. This is an excellent nuke, and very strong early game. Of the two nukes, laser costs less mana, has a much lesser cooldown(you won't have rearm early game), ignores magic resistance(counts as Pure), and blinds/disarms the targets physical attacks for three seconds. This is your primary source of damage, and a good one at that. It has one weakness, you need to get close to someone to use it, usually close enough for them to hit you back. This can mean you trade nukes or get stunned, which neither of those are good.
Heat Seeking Missile
Want to Seek that heat?(No, I'm not alluding to THAT) Then this is the skill for you. This is tinker's second nuke and one with the most versatility and should be maxed out a close second. Like laser, rocket's do a lot of damage, especially early game. They also have insane range, and lock on to not one, but the two closet heroes automatically(they have to be in vision though, if only one is in range, one rocket will be fired). They are quick to fire, so you can shoot these on the move with only a small animation. They are great for poking and pushing back heroes from lanes getting close to your tower, you can just spam them from afar when you're late for a teamfight or finishing off heroes. While they are damn good, they have their weaknesses. They costs more mana than laser, while not doing quite as much damage. They also have a much longer cooldown, and can be shaken off by blink, going ethreal, or by going invisible and can be done on reaction easily. Lastly, if you fire rockets out of range, the mana and cooldown are wasted. As such try to maximize your rockets and there chance of hitting by trying to get two heroes in range and that don't have one of those missile breakers or have already used it.
March of the Machines
March of the machines is tinker's primary source of farm and pushing power. Mid-game, re-arm and MotM become a monster farming tool, allowing you to get the last hit on every single damn creep in that wave almost every time. Early game, you don't have the mana to sustain this and would better used on your nukes for ganking, and at early levels, and without rearm, it won't get as many last-hits as you'd like it too. Further more, your not going to want to push your lane which MoTM will do. Max this out after the nukes and when you have at least one point in re-arm. Some other things you should know that it damages magic immune units, and can be surprisingly effective in team fights when placed at the right time in the right place. Can also deal with those pesky invisibles (*cough* SK *Cough*). I'd also like to mention that this skill is proabbly one of the better counter pushing skills, as it's huge AOE, decent damage and ability to hit any unit makes its very hard for teams to push with a tinker that is supported as it gets rid of both creeps waves and deals very good damage to heroes that linger. No team wants to fight under a tower with no creep support and in MoTM's AOE.
Initializing in 3...2....1..
This is tinkers most unique and powerful spell. Rearm resets the cooldowns on all of tinker's items and ability cooldowns at the cost of mana and a channel time. Essentially, a refresher orb without the cooldown. This allows tinker to get a lot from active ability items more than most heroes. This combined with boots make tinker mobile, and offsets his mana hungry weakness. However, on that same note, rearm comes with a cost. It is 150/250/350 mana to use at all levels. There is no point in using rearm, when after the spell, you have no mana to use left anyway. At level 6, you cannot afford to use this whatsoever, you simply don't have the mana pool. As such, don't get a point into rearm til at least level 9. You should have one point into rearm before you get boots of travel, so use that as a sign of when to put a point into it. After boots, and later levels when tinker has more mana and sustain, rearm because a very useful tool in just about everything tinker does. From dealing damage, to pushing, to mobility...etc. One level in rearm will last you quite a while, you can get level 2 after shiva's, or just wait until after Scythe to max it out. You should have level 2 by Scythe at least. You should have the mana pool and mana regen to afford an extra hundred mana. Now that your in late game you'l need to dish out damage as fast as you can, and a 3 second rearm will not be kind to you this late.
Just note, rearm uses mana when activated, but the cooldown reset doesn't occur until AFTER the channel time. DO NOT PRESS BUTTONS during rearm, or kiss that mana bye bye. You can use shift up commands without breaking the channel.
Rearm doesn't affect all items, Black King Bar, Necromonicon, Arcane Boots, Helm of the Dominator, Hand of Midas....or Refresher Orb are all not affected by rearm. So no, you can't have infinite magic immunity.
Generally, tinker is played has a solo mid hero, but since we're talking about pubs here, a side lane tinker can workout. Personally the skill build and skill order seems mostly the same to me. Whether solo midlane or duo sidelane tinker's nukes should still be maxed first for harassment and early ganks. If your partner has a stun, this can set you up for easy ganks. You could replace a bottle for nulls, or get a soul ring early since your no longer the "rune" guy and will lack mana sustain especially since it will take longer to get boots. The same rules that apply to other side laners still applies to you. Try not to push the lane, last hit and deny, and make sure you pull back when there mid is missing because you are very squishy and have no escape mechanism to save you.
Once you get boots however, I feel tinker plays the same as he would going solo mid first. Your still going to get shiva's and scythe after, and your still going to be farming and pushing. The main difference is that it will probably take you longer to get that point than if you went solo mid lane.