Tips to get fast a lvl 80 partner:
1: recruit 4 blue 1-3 star partner and train them in gym so often you can.
2: use the 4 blue patner, and the red/purple partner you want to get lvl80, in your formation and fight (wipe-out) the bossfights in the storyline.
3: use this formation too after you get event rewards (for example: sea battle)
4: dismiss returns the blue partner if they have enough exp.
1: recruit 4 blue 1-3 star partner and train them in gym so often you can.
2: use the 4 blue patner, and the red/purple partner you want to get lvl80, in your formation and fight (wipe-out) the bossfights in the storyline.
3: use this formation too after you get event rewards (for example: sea battle)
4: dismiss returns the blue partner if they have enough exp.