>>11855915Sevii Islands, Island 1, just outside the Ember Spa.
There are like 5 trainers that you can call with a single VSSeeker use. To heal pokémon you just need to enter the spa pool, faster than a pokémon center. While you run inside the spa the battery recharges.
All the trainers have pure fighting types (machop, machoke, mankey, primeape) at levels 35-40.
Took me about 30 min to get to level 53.
