I'm on mobile so I'm going to summarize a bit. On your first play through I'd really encourage just playing the way you want to play. Be that WT1, WT2 - doing side quests or focusing on main story. Just enjoy it!
The only thing I'd throw in there is that you do have to complete the campaign to unlock WT3 difficulty. If your 50 or getting close and haven't wrapped up the campaign, I would try to shift gears to wrap it up.
This appears to be 3, so mostly rifts and greater rifts.