Dont take this Guide and Champ aggainst everyone!

Gapcloser and heavily burst champs will kill you easily, so it's kinda tricky to find a good game to play it (but it's worth ;D).

But if you have to face such champs (and there a lot of at top) play safe until you have your "W", you wont max it first, but it will be really really important!
Try to escape with it from the main dmg. And here come the tricky thing: Don't just dash away, no no at this point it's time to ENGAGE! Knock him/her up and slap him with your "Q", fight him longer in case of: your jungler is ganking (dont forget your "E" to escape some extra dmg or cut off his/her escape try - or you are sure you dont take more dmg than you are healing with your "Q" and Life Steal, so you can kill him or run away after it.

It's really simple and viable, dont be shy to try something out and run away with your ult.

After your fullbuild you should have enough dmg and sustain to fight any enemy 1vs1, but dont try 1vs2 or more, your kit doesnt gives you a lot of free place for this.

In Teamfights your job is to SUPPORT a lot, your high HP allows you to Ult into the enemy - use your "e" to jump to someone in danger and "W" in again - dont forget that you can use your "E" a second time and jump out again. While you are jumping around you are hard to catch, use this for some extra auto-attacks meanwhile the combo. After you used all your abilitys you can enjoy the now stacked "Rageblade" and slap the **** out of the Champs. If your ADC is still alive and in a good position you should stand on the other side of the fight, so they cant focus both of you. If he/she is in trouble stand in the near to the ADC so you can easily knock the life risk up or give the ADC a shield if your abilitys are no longer on CD ;)

At first, thanks to SlendyJaguar for suggest this variety of my Guide.

Some Stats for beginning:
"Wit's End" will give you:
40% Attack Speed
40 Magic Restistance
40 bonus magic damage on hit
25 MR-stealing fun

Now let's go in the detail:

1. based on the full stacked "Guinsoo's Rageblade" and reached lvl 18, this item will give you additional 0.34 Attack Speed -> so we are a total attack speed of 1.73 (1,39 without)

2. The MR could be really helpful, because Rakan only has 30 basic MR over the whole game.
If the enemy team has got an ap midlaner this item could be worth a lot.

3. 40 bonus magic damage on hit (55 with "Nashor's Tooth") are a big damage supplement.

On the other side we will loose 80AP, and % per health damage.
Also 300 health, which will highly effect Rakans teamfight potential, in case they have a lot of AD dmg.

As you should buy this item at fourth, the 80AP lost won't hurt that much, as long your farming phase is over (should be over at this point).
The %-Damage will just turn in On-Hit-Damage, not that effectiv aggainst tanks but it will help aggainst, for example a fed ADC.

In Conclusion:
This small change can help you win or loose. So decide carefully.
I can recommended this item in case of:
1. There is no Galio in the enemy team.
2. The enemy midlaner depends on AP-Damge or they have an AP-Carry

I hope i could explain this to the most of you.

The import thing here is to take a lot of Ability (I take usually full ap) 'cause you dont get any at the beginning.
I dont recommend to take full AD 'cause it will ruin the spirit of this build ;)
The little Armor or MR you could carry wont make that difference, you should rely on your healing power, but you can take some mana reg.-runes if you cant deal the mana household.

Ferocity:
Take "Fresh Blood" if you think you shouldnt have that much trouble in the lane, but if you are not sure take "Feast"
You dont need the life steal mastery because you'll start with "Dorans Blade" and next take "Battle Trance" 'cause you'll have to poke and jump in for the rest, the rest wont help you here.

Cunning:
I am a fan of "Wanderer" 'cause you can spare sometimes your teleport to help bot with your Ultimate.
The Cookies are helpful for your Mana, but arent necessary if you can handel it.
The next one is really usefull after your pokerino for execution.
"Dangerous Game" will be handsome in late, when your first duty is to protect and dealing some "underdog"-dmg.
Take "Precision" or you will loose a lot of free dmg.
"Thunderlord" will getting usefull in late 'cause your attack speed. You can also take the healing thing for late but then you have to play a bit more defensive, and who wants that?

Your "Q" will be your sustain tool AND your damage -> you should max it first
You can use your "W" to stun your enemy, hit him with the "Q" and make a run (dont combine it with your "Q" if your enemy has a burst range/gap closer Champ: in this case you have to use it max range)
Or use "W" if the enemy jungler is ganking you, skill it earlier when it seems he comes in the next time
Your "E" is getting interesting at lvl 5 and 6 cause this is the time your jungler may come and gank, i think you know what you should do at this point

Pros:
1. A lot of outplay potential
2. Strong Mid and Late Game
3. Affective after the first item
4. Good sustain
5. High roaming possibility

Cons:
1. Weak at the beginning - try to farm a lot
2. You will hear this annyoing Slap-Sound really really often
3. Without good positioning you'll fail like an ADC

Without the Spirit of Teamwork this champ isn't for you.
Your Kit is perfect for Roaming, but dont invade the enemy jungler without backup!
Help your Jungler, Mid or teleport at bot - your spells are for every situation.
Your Top-Enemy is back, or somewhere else and your minions are already at his/her turret, feel free to give vision about their top-jungle, but don't forget to ping your midlane, a friend in the near to jump to can save your life many times.

Be sure this Guide works for you fine, or change it the way you need it to be before you try this in ranked!
But sure it is possible aggainst the right enemy - don't pick it blind.

Good Luck!

If you have some ideas to this build write me a message so I can update it ;)
Feel free to write me if you have questions.

Have fun and enjoy your day in the rift and never forget: It's just a Game, play in the way you AND your teammates have fun in the round; This is the Goal for every Game.

Changelog:

+ alternate build
+ some fixes