I run a rune page with full flat ad marks and quints with flat armor seals and magic resist per level glyphs. The flat ad helps tremendously with last hitting and can help you harass the opposing carry. The flat armor seals also help with trading as it gives you the much needed armor at earlier levels against their ad carry. The glyphs are pretty obvious as they help you scale mr into late game. Alternatively, you can run armor pen reds and attack quints or attack reds and armor pen quints if you feel that armor pen is really important to you.

Masteries are pretty standard. 21 in offense taking the necessary stuff. I go 9 defense as it gives me some armor, hp, and the improvement to cleanse. If you feel like running cleanse is a hindrance to your play style, you can run exhaust/ignite and take the improved summoner spell in offense while taking 9 in utility, grabbing rune affinic. I recommend getting 9 defense as it gives you more hp, armor, and if you run heal/cleanse, you are much more safe in lane in the case of high aggression, a gank from mid/jungle, or your support being complete ****.

Items are a standard ad carry build. Go boots three for the improved movement speed. Don't ever start doran's unless you have a soraka, and even then i never get it. The additional movement speed to help last hitting, the movement speed to escape ganks and trades, and the pots for sustain just outweigh the benefits of grabbing a doran's for me. You should head back as much as needed. Having more items then your opponent will help you establish lane dominance but this doesn't mean to go back every wave you clear. Be smart and pick reasonable times to go back. I usually go back when I have around 2000 gold. I pick up two doran's, greaves, and a vamp scepter. This helps with farming and sustain still and at this point, its all you should be worrying about except the occasional dragon and ganks. You should aim for 2000 gold again as you go back. Buy your bf sword and wards or pots you need. You can go back whenever you like now as long as you have enough for a pickaxe or the infinity itself. This is the bread and butter item for twitch. Next a zeal should be enough attack speed as your q passive is already strong as it is. You should now be aiming for defensive items. I always get qss when there is a bunch of crowd control on the other team. You disable=you not dealing damage=you lose. If you find that they don't have a lot of cc, banshee is always a nice item. Some other great defensive items are thornmail and guardian angel. You should now top off your build with finishing your zeal into a phantom dancer, a last whisper for the armor pen, and finishing your vamp into a bloodthirster for sustain and life steal.

R>E>Q>W

You can run cleanse/heal/ignite/exhaust but flash is a must.