TIPS:

Use flash before jumping with W for extra range. What you should do is FLASH > W, and not W > FLASH as you may not hit the target with your W.

If you are out of combat, always use your W (W that makes you ride the horse), because it makes you faster + lets you jump faster (without it you would have to press W 2 times).

Your basic combo should look like this: W (jump) + Q + E
Combo with R: W + Q + R + E
Combo with R while chasing an enemy: W + Q + E + R


Early game

If you start by blue side:
Start blue by Q and cast it 2 more times. DONT SMITE!! You will need smite for scattler later. After blue get E and go gromp. Use e everytime u are able to, as its one of your strongest spells. After gromp go wolves.

After doing blue side, you may look for early ganks on bot or mid. Every early gank should work because your q and w is really strong. If theres no lane to gank, start red side by raptors. After that, go do red (you can smite it) and scattler if it had already spawned. You can do golems after scattler (cause scattler is more important). Expect duel at river for scattler. If you manage to take the first scattler, run to downside of the jg to take 2nd one. If you do so, you should come bot to create some pressure.

If you start by red side:
Start red with Q and dont smite, you will need the smite for scattler later. After doing red upgrade "W" and jump into golems through the wall. After golems go for raptors with your W.

After doing red side gank mid or bot if its possible. Rell has good early ganks and its easy to create pressure with her. If theres no lane to gank, go to the blue side and start wolves by jumping with your "W". Then, go blue and smite it, and go gromp without smiting him. Smite scattler instead. If you manage to take the first scattler, run to downside of the jg to take 2nd one. If you do so, you should come bot to create some pressure.

(Note, that rell W can jump through small walls, so its really helpful when u gank)

Mid game

Farm alot untill you have Any of the core items. Your damage with E is very strong, so you may win duels with enemy jg. Dont engage 1v1 with him though, as you should play as safe as you can, looking for easy ganks. After drake spawns gank bot and then drake, rell has good clear and good damage to epic monsters, so you should do it really quickly with your bot.

Late game

Engage every teamfight by jumping in enemy team with your W and R. Look for easy kills on off lanes. If you have 2+ items you should win most of 1v1. Remember to push alot, as you deal big damage to turrets with your E. Every time you win type in chat "jg gap".