Alright, just a fair warning to you PC folks that's still below 60 stages: beware of Gastly, Raichu, M-Altaria, M-Mawile and M-Glalie stages. I think I can provide a few tips for those stages.
Gastly's disruptions allows you to only use the top 2 rows of the field, and since the Pokemon's locations are randomized, there's no certain trick into winning this.
M-Altaria, I have vague memories about this 'cause I got lucky and got it on my last turn. Just... beware, you'll probably have to fail at least once or twice before winning.
M-Mawile... Just roll with super-effective moves. Don't even think going with M-Sableye 'cause it'll be completely useless against the disruptions M-Mawile will shower you on that stage. Don't mind using Megas at all. And probably get a Move+5 while you're at it.
Raichu... okay, M-Kanga is the best thing for this stage unless you're willing to sacrifice 2/3 slots for Pichu and Pikachu just to get rid of the barriers. No, really. It's that bad. I mean, with a set up like:
xoxoxo
xoxoxo
xoxoxo
xoxoxo
xoxoxo
xoxoxo
With x being the Chu line underneath barriers and o being your own Pokemon, that's a really limited space to play on. Did I mention the default catch rate is 3%? Yeah, have fun repeating the stage over and over again.
You'd be so lucky just to get a freaking C on any of those stages.
I just reached M-Glalie myself after going to the web and seeing how many people ranting on the difficulty. And after reaching the stage myself... man, M-Mawile looks a lot more simpler than this monstrocity.
This is coming from someone who has caught all the Expert Stage Pokemon up 'til Sceptile.