With W13 on lock you can start getting proper gear for all your units. How long does your run take and how stable is it? Given how much time you spend in W13 I'd maybe say making your runs as fast/stable as you reasonably can now is a good investment.

After that depends what you want to do. Do you have good PvP teams for GW, arena etc? RTA probably comes later. Make sure you can do expeditions at least at lvl 2. Push abyss maybe?

With W13 you've gotten out of the early game, so now the question is what parts of the game you want to focus on. Plenty to do in both PvE and PvP if you want.

As a short term goal I'd maybe say try to get Masters 5 in arena, it's relatively easy and you can't decay out of there, and you get 600 skystones per week for free in that rank. You could probably do a bruiser team with Ruele + Delibet + FMaya + (Ken or Mort or Senya), or a cleave team with Vildred + Eda + (an opener with a non-attack skill for Eda and a speed imprint).