This is my first build with any champ so let me know how it is. Cait is one of my favorite champs she has great range and with the right attack speed I don't think anyone should have a bad game with her escape abilities.

At start I prefer to take mid if I can because Cait needs a lot of farm to get good early kills and become unstoppable. I usually use my Q for harass as much as I can early without getting in mana trouble. You should only use it when the other champ is coming in close or no minions are between you. It will deal more damage and give better harass so you will not waste as much mana early. Try to last hit minions as much as you can and when your passive procs use the extra damage as harass. I have seen too many players waste that shot on minions and think Cait does no damage. If your doing this right you will force your opponent to either go back early or give you an easy kill with your ult at level 6. I usually do not go back to buy until I have enough money for my second blade and my second tier boots. If you can help it try to stay in lane until you can grab your vampiric scepter as well. Then get back to lane and continue to harass and try to push tower if you can. As with any champions wards are your best friend mid if they have a jungle its double important.

Now you should be working towards your first bf sword, this is important because it will give you the extra damage you need to finish guys off. If you have pushed your tower down or your teammates are having trouble get to ganking. You should remember when you go to gank to lay some traps behind you in bushes so you do not get countered as easily. I prefer to come in from river bushes and drop traps there since most champs come in from that way. Since your ult is not as reliable as some other champs because of how easy it is to jump infront of do not get mad if you hit another champ. Just spam it when you get it because it does good damage and this is a team game so if you help a teammate get a kill that is just as good. Work towards your bloodthirster fast because the extra lifesteal is great. Most people I see playing her do not go with much lifesteal but I think lifesteal and attack speed on her are a great combo. If your doing well on kills try to work on your phantom dancer its a great item for Cait.

Now you should be getting more into team fights. These are where you shine. As with most ranged ad carries you want to stay in the back and pick off the damage dealers for the other team. You have good lifesteal and damage so you should not be in much trouble, but if you are getting targeted use your E to get back and try to come around from a bush and let loose on everyone. When they enemy thinks you have to go back and you can stand in a bush and get your life back you really will turn the tide of a battle.

This build should give you the chance to change games with Cait. The way I run it I use the mass attack speed to get your passive off as much as you can and the high lifesteal will let you get away and come back into battle without going back to heal in the middle of a battle. Cait is a squishy champ so she will get targeted fast, but that is where your biggest advantage will be in getting out and finding a nice bush to take out the other team from.