>>43933398You can enter the DLC one you have access to the wild area.
You can go as soon as that, but you can't complete the DLC's story unless you have the water bike, which you don't get until after the sixth gym.
The scaling is based on badge numbers and with all 8 badges most pokemon cap at around level 60 except the giant whale in the water that's level 80. The story battles shoot up level very quickly despite there being so few of them, so you might have to grind if you start with a level 60 team. The final battle of the story is level 75.
