Pokerogue for newbies?

Got back into the game after a large break and so much has change so I was wondering if people could help with some questions (since most answers to them seem to be outdated?)

Farming
Where and how is the best way to farm candies/egg tickets? I've seen people say Endless and others Classic for both answers and was hoping someone could dispel the doubt for me.

Good Mons
I'm struggling with consistently clearing waves (I'm pretty bad at pokemon) and was wondering if I could have recommendations in terms of strong pokemon to invest on?

Shinies
Is the best way to acquire them through tickets or is there another more efficient way to try and hunt for them? Is there a way to hunt for a specific mon's shiny or just sheer luck?

Thanks in advance if anyone answers some of these questions much appreciated. Also as a throwaway suggestion, It'd be cool if we could use Candies to increase the base PP of moves in some of our mons don't you think?