Weapons level up to 20, you can then reforge in the middle of town to lvl 1 for Aetherhearts which can be used to power surge weapons and armor to make them stronger. Also, leveling up weapon bonuses on your slayers tree. Those bonuses work with all weapons. 10 reforges per weapon are useful in that regard, but you can keep doing it.
Beyond that, hit "M" in town for the map. Behind "Arkan Drew" (the lantern) there's a machine you can use to set bonuses for escalations (you can level up to 25 for each escalation type).
Things to do -
Escalations for runs with several behemoths (1-13 is easier, 10-50 usually helps to have a lot of levels unlocked).
Join people in hunting grounds islands.
Focus on quests, bounties, and challenges "U", don't forget to check the "Reward Cache" under "Challenges" (or "P") there are 6 days left on the current coins/things to purchase.
I just realized I gave all PC commands, but these should be findable in the menu if you use a controller. If you have any questions, feel free to ask. Also, welcome back!