I am bronze and I made this for fun. I play rell for most of my jungle games, but I am not a jungle main. Take these advice at own risk.

Pros

Lots of utility
CC chains
Good if team has no frontline
W gank
Basically a 2nd support for ADC
Doesn't matter if behind, mostly used for utility
Good for stealing objective

Cons

No damage
Relies on team to do damage
Takes objectives slower
Is basically only a 2nd support
Isn't a carry character

Phase Rush
Need that MS
Nimbus Cloak
For moving between camps after using smite
Need that MS
Celerity
Good with E
Need that MS
Waterwalking
Good for ganks
Need that MS

Hextech Flashtraption
Good for gank or steal
Cosmic Insight
Haste!!!

With leash:
Start Q
W
E
Max Q for cooldown reduction
Max W next for cool shield
Max E last

Without leash:
Start W
Q
E
Same as before

Q actually has a pretty long range, don't afraid to use it. Even if you catch someone at the tip of your Q they are still stunned and you can W for follow up.

W gives shield and airbornes anyone hit. It also allows you to go over walls and get out of situations. This makes it one of the best abilities for stealing objectives. If you have vision you can wait for the right time to W in and steal.

E for chase.

One of the strongest teamfighting utility wise in the game. Rell can easily CC the entire team if she catches them in the ult. Flash + R for element of surprise and then follow up with W and Q means an easy CC chain. You have to make sure your team can follow up though.

If your teammate has an aoe ability with skillshots you can R to make targetting easier for them.

A lot of people don't like support junglers and thats okay. But remember the whole point of Rell jungle is to help your carries do their job.