If you are playing Caitylin I suggest that you play as ad carry at the bottom lane. When it comes to items you should first buy boots of speed and 3 health potions. Then but vampiric scepter and a zeal if you can. Evolve your vamipirc scepter to a bloodthirster and then buy berserkers´s greaves. Next time you are at base u should buy the phantom dancer and start buying your infinity edge.

Start and max your Q and then your W. Upgrade your ulti as fast as you can. Caitylins E is only needed when u have to escape a dangerous situation or hunt someone down, but you ca do that with your ulti so I dont recomend it.

You should always farm from the bush, because of your passive. your passive charges up faster if you shoot from the bush.

I usually use flash and ignite so I can hunt/escape, finish them of if I can´t towerdive them. Another option is flash and exhaust. Exhaust smallers the damage from the enemy champion and slows them. It is very useful against other AD carrys in 1v1 situations