Pros
1. One-Shot potential.
2. Assasin and Bruiser build options for different drafts.
3. Easy to learn, hard to master.
4. Easy to gank with R and W.
5. Can easyly execute low HP targets in teamfights with Q/
Cons
1. Very bad scaling.
2. Cant kill tanks and beefy Bruisers if not fed.
3. One-way assasin - its easy for you to engage, but hard to retreat. Think twice before using your W.
4. Really reliant on hitting Qs - at the moment your enemy dodges your melee Q, you are dead in 80% of situations.

On Red side, I recommend you to do Blue buff and camps first if your botlane has early CC(like Lux, Morgana or any melee support). In other situations, where you have supports like Lulu, Soraka, Yuumi etc., you should go for your Red Buff and camps and look for early gank on top- or mid- lane. Gank botlane only when you have Ult or when you need to take drake.
On Blue side, always take Red Buff and camps, and then look for gank on botlane (if your support has early CC) or midlane.
Early ganks is not alwats viable, but I recommend to do it in most of your games. After getting your R at 6 level, you can do a little trick - gank lane and then use your ult to go for and object on opposite side of the map. This is a fairly obvious trick, but a lot of junglers, even at a high elo, fall for it. For example, you can gank toplane and then use your ult to land on a dragon.

As an engage assasin with a lot of one-shot potential, your first and the only job will be killing enemy squishes. Be sure that you have a teammate near you who can cover you after engage or provide a good CC so you can run away. In massive teamfight you can flank and look for a surprise kill on enemy ADC. Also you can start a teamfight by yourself with your R, but be really careful and fully aware if your team location.
If you dont have a reliant tank or bruiser in your team, I higly recommend you to build bruiser build, but you'll still be really squishy and can be easily oneshotted with one CC chain. Look for a teamfight where your support or midlaner alredy CCed someone, so you prolong with your W, kill and then retreat.

Thank you so much for reading this guide. This was the first guide I had written in my entire life, and I tried to explain everything clearly and in detail. Also, I am weak in my knowledge of English, but I still tried not to make mistakes in speech. If you liked or disliked this article, write a comment and rate it accordingly. I hope to hear constructive criticism so that I can supplement or correct this guide.