I finished this game and all but, I am still wishing to train my Pokemon a lot
I know that
There is my team, moveset and natures
I got all starters by trading
ALL MY POKEMON ARE MALE EXPECT FOR RAYQUAZA SINCE IT'S GENDERLESS
Ability: Air Lock
Ability: You know its ability very well
I have rematched Wally, few gym leaders and defeated Elite Four a lot of times but, it doesn't give my Pokemon a lot of EXP
I just want high level so I can be ready for open level frontier brains and is there any place or way to train this team?
Sorry I gave some of them useless attacks
Pelippers have a 5% chance of holding a lucky egg in the wild, so you can attach a lucky egg to a Pokemon so it has 150% of the gained XP. Once you've done that, you can go through victory road and battle every wild Pokemon you find until you get to the end. Once at the end, you can battle the elite 4 and wally as you said but with 150% XP on all Pokemon that entered the battles and are holding a lucky egg.
Hope I helped :)