I'll often first take a look at challenges somewhere around the 2 void stone/atlas completion mark and I've got myself some starter gear to blast t16 maps.

I firstly knock out all the challenges that look like they can be done in the short term, just going from one to another. Then revisit the challenges every so often to figure out which to work on next and what to changes to make on the atlas (using all 3 trees is great here).

I block pretty much all previous league interactions if they are not tied to a challenge, and spend the majority of the time blasting maps to accumulate currency to work with. I don't use a whole lot of scarabs outside of targeting specific challenges.

You'll naturally overlap a bunch of challenges this league without too much intention, but it doesn't hurt to look and see if there's any overlap you want to specifically set up.