Pros:
+ Has great CC and damage
+ Gives teams great pick potential
+ Amazing clears once you get a few items
+ Insane map presence and gank potential with ult
+ Has a huge powerspike when you get ult and Runic echoes

Cons:
- Can be seen by some as a "Troll pick" if you fall behind
- Can become dangerously low first clear and you may be executed if you do not kite well and path correctly
- Highly susceptible to early counterjungling

To make this work most efficiently, you will have to use a specific jungle path and make sure to use your abilities exactly as required.

Your path will be:
Kruggs (smite) -> Chickens -> Red (smite)

Kruggs:
Smite the kruggs at the start to ensure your first autoattack stuns them. Proceed then to lock in a gold card, stunning the kruggs immediately again. you should then kite them around spamming blue cards and use one potion charge. Be careful to not drop aggro (This can be seen in the patience bar, if it starts to drop, let the kruggs hit you once and then start to kite again)
You should still be relatively healthy after this camp (usually around 75% if done correctly)

Chickens:
This is where the AD reds help hugely. Lock in a red card and throw it at the big chicken and move back slightly. The small chickens should line up while running at you, allowing you to Q through them all. After the AoE from the red and the Q, each small chicken can be killed with one autoattack, leaving only the large one for you to kite and again spam blue cards.
You should take little damage from this camp.

Red:
As with the chickens, throw a red card and Q, making sure a card hits each monster, then kite out the red, use another charge of your pot and smite red when you are just under half hp for the health regain.
It is highly advisable to ward over the wall of red into the bushes towards your jungle entrance from the river, as you may be invaded.

You should then back and pick up the hunter's talisman.

Blue should be the next camp you clear, opening with red card and Q again to maximise your damage.

You now have the choice to either smite wolves to give you vision against invades, or Gromp to give you a slightly easier time clearing.

Once you get your rod, you should oneshot the small monsters with Red + Q, so farming becomes incredibly easy.

After you have cleared each camp, you can proceed to gank a lane, take the scuttler or go back to kruggs and work your way down your jungle.

Pre 6 you should play defensively, warding to avoid invades and focusing on buying your jungle item.

Once you have Runic echoes and your Ultimate, you should heavily farm camps while your ultimate is up, and prepare to countergank or gank your lanes. Gank while the enemy laners are overextended past the halfway point of the lane. This gives you chance to gold card twice, highly increasing the chance of a successful gank. If you use the runes recommended, you should always be able to chase down enemies due to the movespeed quints. You should run along the lane alongside the enemies while attacking them, keeping as small a distance as required between you.

Skirmisher's sabre is the smite I would advise the most, as it greatly helps to cover up Twisted Fate's squishiness early on, reducing damage dealt by the smited champion by 20%.

When your ultimate is on cooldown, you should try to gank and use the powerspike that runic echoes gives you efficiently, while still farming when you can.

Flash + Gold card is commonly used by most TF players, but is often not used to its fullest potential, if buffered correctly you will still stun the enemy if they flash away. To do this, you need to right click the enemy and then flash without issuing any movement commands. The autoattack will start instantly after the flash.

Once you have Zhonya's Hourglass, you can ult in with a gold card and instantly use it's active after throwing the card to set up an engage for your team. You can also use the Zhonya's active during the channel of the reactivation of your ult to bait out big spells; as most people will use skillshot stuns and damage abilities on the cards which show where you will appear. This isn't usually the most efficient use of zhonya's and ult, as you will stay in your original position, however it's something that is incredibly useful to know.

Remember to practice your clear at least once in a custom game on your own to make sure you have it correct and you should have no problems then on :)

For people wondering how viable the build is, I recommend you try it and see for yourself, I play this regularly in ranked with good results.

Most people will go devourer on TF jungle, but the idea is similar to buying warrior on kindred; you get an early game powerspike that you can use to snowball your lanes as opposed to being required to farm heavily for your stacks and not exert as much pressure on the game.

If played correctly, this build can let you oneshot squishies with your combo in the lategame, while still being tanky enough to survive prolonged teamfights with lots of poke.

I will add more to this guide in the future, as this is a very brief overview, but there should be enough here to manage.