Without counting Pokemon League and Stadions.
Black Tower Victory Road Cloress Straiton City ex-gym leaders Cynthia N Shadow Triad White Forest Castelia - Royal Unova Join Avenue - the Fitness counter there
Depending at what level you are:
Route 23 - Audino training with Lucky Egg Nimbasa - Little Court & Big Stadium, once a day and you get a ton of cash + some items too. Plasma frigate (near P2 lab) - Colress, once a day.
Colress at P2 Laboratory with lvl 77-80 Pokemon. In Castelia City with the two game freaks with lvl 74-78 Pokemon. Or the royal unova with lvl 65-68 Pokemon. You need 1000 pokedollars to get on. In nimbasa city with the big and small courts with lvl 60-65 Pokemon. Your rival in Driftveil city with lvl 66-70 Pokemon. Audinos with lucky egg. Black tower. Striaton Gym with two on two battles with cilan, cress, and chili with lvl 65-68 Pokemon. N at victory road with lvl 70-80 Pokemon. Join avenue with the deli person and fitness trainer. Make sure you have a lot of money though. Cynthia at Undella Bay with lvl 74-80 Pokemon. The shadow triad at Iccirus City to to the right of the Pokemon center over the bridges. You will battle all three of them with lvl 74-78 Pokemon.
