Looking to get into PVM, using league for first time experience, what regions should I pick?

Depends which bosses you want to get hands-on with! Pick stuff you think looks cool in videos you've seen and just pick those regions + have fun! Can't go wrong with Raids regions (Morytania's probably got the coolest offerings on that front with TOB, GGs, Nightmare/PNM, Barrows, Araxxor)