Due to Wild CardsWild Cards having one of the highest non-global non-ultimate range in-game, he can harass very well. This makes him a good pick for mid lane. While the projectiles are slow moving, the long range of the cards often catch enemies by surprise. Additionally, the projectiles, unlike many skillshots and pokes, will pass through minions, and even do damage as multiple targets are passed. This disallows opponents from blocking with their waves.
The card last chosen can be the first card available when Pick a CardPick a Card is available again. Despite locking a specific card, the ability will still cycle the card rotation every time the card above Twisted Fate pulsates. Thus, if you throw the desired card immediately after locking it before it has a chance to pulsate again, or every three pulses after locking it, the next card will be the one you last locked.
Even if you will not manage to immediately grab the exact same card, counting the beats after the card you chose can still tip you off toward grabbing the same card again from the current card for the next time you activate the ability.
Destiny and Gate can be used to quickly backdoor enemy structures. Used in conjuction with another great backdoor ability, Pick a CardPick a Card, as the bonus damage is applied to turrets, it's pretty difficult for enemies to defend.
Map awareness is key to proper use of Destiny. Look around the map carefully while farming or traveling for potential foes.
Be sure to ping onto targets just in case your allies don't have the same map awareness as you do when you plan to use it! Twisted Fate using Gate against a sole target is unlikely to work well while the cooldown of Destiny is fairly long for a lot of the game.
Keep in mind that Destiny will pop your enemy's Banshee's Veil but this will also prevent him/her from being revealed by your ultimate (you can still use Gate though). Meaning that against a team with multiple Veils, you can use Destiny to pop their shields before a big teamfight. Be warned that fleeing low-health enemies will likely be guarded by their allies that remain invisible to your ultimate (and you will only know it after teleporting to kill them and be ganked yourself). Coordinate with your allies for the best time to use Destiny to ambush enemies.
In a pinch, try to either juke your enemy and then run into a bush, or stun them with Gold CardGold Card. If successful, pop your ultimate and start teleporting away with Gate. By the time the enemy has a chance to attack you again, you should be a safe distance away. This technique can even work out in the open without Gold CardGold Card if you wait for the enemy to pop all their crowd control first.
Twisted Fate is relatively fragile at early game, putting an aggressive pressure on the lane can make him underleveled or underfarmed.
Twisted Fate has fairly poor sustained damage with an AP build - if you can get movement-affecting crowd control on him before he stuns you as a champion with a greater sustained damage potential, you may be able to turn the trade in your favour.
When you are under the effect of Destiny, be prepared for a gank as his Gate allows him to teleport to a huge range in the map.
Gate has a noticeable channeling with a marked location - this can leave him an easy target for skillshots. If the skillshots apply crowd control, this can stop Twisted Fate from getting you killed - or maybe even turn the gank onto him!