You will be last hitting minions with blue card as soon as you reach level 2 and at level one you will try to harass as much as possible against the opposition. If your opponent is around half health when your level 5 and have a full stacked deck Flash in with gold card equipped and grab the kill with an Ignite and Wild Cards, When you reach level 6 I recommend you gank depending on the state of top and bot, if you gank bot you will give your AD carry the upper hand and immobilising minion farm from their AD carry.
You should have Rylai's Crystal Scepter after your ganking this will help you not feed and provide enough AP to burst down the opponent. Around this time team fight should be more frequent, help out your team by stunning the AD carry and staying out of range of the opponents and in range to land Wild Cards. Wild Cards will provide enough burst so that you can grab the kill.
You should save your ultimate for ganks on top and bot for defending top and bot turrets, to increase vision for your team and see the enemy team or to chase down a low health opponent.

You will start with Boots Of Speed and 3 Health Potions, try not to spend all your Potions in one go. You will follow on with two Doran's Rings which will help out allot to earn kills by increasing your early laning phase with these Doran's Rings you should be able to grab a kill when your opponent is half health and you have your gold card. Next you'll upgrade your Boots Of Speed to Sorcerer's Shoes and start building the components to your Rylai's Crystal Scepter, as soon as you've built Rylai's you should have enough AP and health to grab one or two kills from top to contribute to your Rabadon's Deathcap. You build Rylai's first because Twisted Fate is very squishy and needs some health to fend off the enemy mids harass and provide allot of harass.
After Rabadon's you will buy yourself a Lich Bane which is very useful for Twisted Fate because of his passive Stacked Deck it also provides allot more damage output against annoying melee mids like Katerina or Akali. When you have enough gold finally get rid of a single Doran's Ring and replace it with Athene's Unholy Grail which provides you with Cooldown Reduction and Mana Regeneration and allows you to take more harass from AP champions. Finally you will get rid of your last Doran's Ring and trade it in for a Zhonya's Hourglass witch gives you some AD protection and AP also you can use your effect for it to either disable other champions attacks or to resist dying.

I suggest you take flash to either initiate during Laning Phase or to get away from ganks also take ignite for the early game harass or when you are initiating a fight with annother champion.