iron island or upper level mt coronet
use the exp share
i recommend the restaurant near lake valor
elite 4
elite 4
An area with grass Pokemon would be best.
the elite 4 or the places with the highest lvl wild Pokemon in them
Route 201 or 202 or 203
Anywhere that u find Pokemon that are close to the shromishes level.
the place where you can breed Pokemon next to heart-home city, that's where i go
easiest way to train your Pokemon is by batteling each trainers or you can practice with wild Pokemon in the grass,cave,or sea
i trained mine at mt.cornet
Stark mountain battle about 7 Pokemon then it will be level 73.