[Brilliant Diamond & Shining Pearl] The best way to 100

So for anyone who wants to get their pokemon to 100 this is the best method I have found so far. You can battle the gym leaders once per day that alone will gain you a ton of exp then once you do this go to the elite four and keep battling them over and over. it is a grind but I was able to get at least ten pokemon including a legendary to 100

of course it also is a good way to make tons of cash while leveling up giving your pokemon the amulet coin as you train i get usually about a little over 100,000 from the elite four from one round with them all but make sure your pokemon are also holding the lucky egg as well.
I just chose a pokemon to level up first then if they can't hold their own switch to a pokemon who has the amulet coin at least once per battle

It honestly didn't take as long as I expected

If only I could rebattle gym leaders before beating Cynthia, since I need to train to be able to beat her! This helps to know for later though, thanks. \o/