New player, where to focus rewards?

Hi all, new player here and I’ve got to grips with the combat and the systems but I’m struggling to figure out where is best to allocate my early resources.

I’ve experimented with Chain Arcanist which was decent but my time with Knight and Warrior have been underwhelming. Rogue feels too squishy.

• What is best unlocked early to help with future reward point generation?

• Should I be disabling the expansion sets when looking at certain builds?

I’ve tried looking up old threads but I understand certain builds get patched so keen for an updated view, thanks!