Veno can be a support like very few others. it is important to follow some very simple things to make him the most useful support on anyone's team. First you have 0 health... 0. you will be ganked relentlessly if you do not ward and watch your surroundings. Ward. Biggest problem I see in pub games is no wards. Given a good lane with a partner who has an idea how to last hit, venomance can be dominating.
If there are two supports and you can talk the other one into getting the courier, you should focus on getting bracer early. There is a large population of venomancers that are trying to be gankers and pushers. This guide is not for them. This guide is for the people who want to get 10-25 assists a match. I prefer pipe of insight to mekanism, but you can't say always get this... because the other team gets to pick their own champs. If you are going against int champs, pipe makes a lot of sense. mek makes a lot of sense when you have a ton of cash early.
big agi items are expensive, and its hard to save the kind of cash needed, when veno will be eliminated after his ult in most team fights. stick with wards and good map awareness. buy two bracers if you need to just to keep alive to the team fights (at that point, you are dead anyways).
Lane Choices/ Lane Partners
Generally, supports get very little choice which lane they are in.
If you are in the long lane (the lane with the jungle camps), you should be stacking the hard creep camp and drawing minions to it every time possible. This is your denial of minions to the carries on the opposite team. You should last hit every one of these neutral creeps. This is your money for courier, wards, and what little items you will have.
If you are in the short lane, you should be aiming to deny every creep you can. your job is not to last hit enemy creeps, but to kill your own. This lane will be hard to get money, hopefully early kills will allow you to get the money needed to purchase your items.
melee champs with mid game or hard carry is who you are trying to lane with. If you are lucky enough to be paired with a Juggernaut, congrats, you just got first blood. The slow from gale (and DOT) combined with Juggs spin move will kill most champs at level 1.
If you are laning with a ranged champ, you should take the long lane, allowing the ranged champ to use the turret as defense with carries (drow), or allowing the ranged champ to push and farm heavy (gyrocopter). Pulling your creeps into the neutral camp will allow the enemy creeps to push out and allow more farming for your carry.
You have very small amounts of mana and health early. dont spam gale unless you are going to get a kill. Every gale should have a purpose. Gale should be to escape from trouble or gain a kill.
If you watch tournaments, pro matches, 5 man teams, they work veno differently with skills. This build is for public games. The build does not go with stats after capping wards. After getting your wards capped, poison touch will help you split push lanes when the other team has lost some champions. Your goal will to be with your team after you get to level 6. Your ult has a wide range (wider than the animation) you should open fights with this. if your team has a tide hunter, you have a small chance to escape from using your ult.