In the mobile version, unfortunately, Bursting/GST does not work to lvl up, HOWEVER, there is another way of lvling up very quick once you hit at least lvl 42.
It's a Suicider train and you will need a few things to know and required to do it.

Needed: - IM bow (6ss for +3 or 21ss for +6)
- Arrow rain skill
- Fast earth OR a lot of HP on your main

This training can be used for mages and for killers as well.

If you're lvl 42+, go to Oslya, Arez quest (the raptor fights, where you see rows and rows of raptors)
Why lvl 42? Because highest lvl raptor is 61 and so you need at least lvl 42 to keep your EQ safe, so it won't break.
Preferably you need an Earth suicider who is fast and has some HP and won't spawn when all raptors hit him at once!!
That earth will put shield on you with remote, but carefully set it for SP to wall you and not HP, or he will wall himself!! Then you can kill the raptors with your +3 or +6 bow.
If your earth is too slow, raptors might attack first and kill you and your earth before he can wall you.
(The difference from +6 bow and +3 bow is that +6 hits more than the +3 bow and the higher it is, the lesser you'll miss on high lvl monsters)
REMEMBER: The Suicider earth HAS to be the LEADER and start the quest and it HAS to die during the battle!! So do not heal him, he must die during the fight. Do not revive him either!!
This way, you can redo the battle over and over again and gain alot of exp. If your earth doesn't die for some unexplained magical reason, do defence on your main so that raptors have a chance to kill your suicider during the fight.
This is needed to be able to redo the quest a lot of times.
If you get to a higher level, you can go to the P quest in Welling Village and do this over and over again. The pirates quest is the one on the far right of the village where there is a trap on the floor, you have to speak to the guard next to it to have it open so you can go inside.

Extra: Close your battle and pk in settings so that people won't revive your Earth and screw with your training!!

Extra extra: To gain gems quicker, have two characters on the same account doing PvP and opening the daily gifts as the gems are shared between characters. In a few weeks, you'll afford the bow if you can't recharge. Also, don't forget that at times, they offer free gems with some updates. Rare, but they do at times.

I thank my friend for this guide and those who added details about it in the Discord group

Also, check the FB group for more details: https://www.facebook.com/groups/224245151317761/