Diablo Game Questions Just finished Campaign, now what?

Alright so I'm done with the Campaign (played through on Expert), now I'm Level 68 and I have Adventure mode.

How do I go about playing Adventure mode? There's bounties, rifts and what not but I'm not sure if there's like a proper way to go about playing them.

Should I start on Act I? I'm not sure!

Basically can I get a quick rundown on how exactly to go about playing Adventure? :D

Should I increase difficulty to Torment for loot immediately? So many questions!