That depends do you want to train it normally or are you trying to EV train it?
i want her to be as strong as possible with normal training and ev trainging oh and let me list every thing about her
OT:modest
level:28
hp:100
atk:42
def:54
sp.atk:72
sp.def:80
speed:59
For a level 28 Milotic her stats arent bad. Now if you'd EV train her she would be a beast. That HP can hit the 380s by level 100. But if you are training it normally go thorugh the Pokemon League. For quite a powerful Pokemon she only needs 600,000 Exp points to be at level 100.
You want a Special Sweeper right? Fight Gastly in the Old Chateau. They give one Ev point for special Attack.
Need some more Defense fight Geodudes and Onixs as they give one defense EV.
Need special Defense fight Tentacreuls on the ocean which give 2 Sp. Def EV points.
For HP go with Woopers west of Pastoria City.
cool thanks and if you dont mind im going to add you to my friends list