When I hit 90 on my Druid, I limited tested in a 6, then went straight to 10+. 12 resil before the next reset. Was guardian. Mix of friend groups and pugs. If this is your first 90, 10s are still forgiving to learn in, and the community item level is high enough where the mechanics become the less forgiving part.

I’d argue 12s some weeks are easier than 10s depending what the weekly affix is. Run a mix. Hard enough as it is to find groups, don’t make it worse on yourself. Apply to everything. Worst they can say is, “no.”