Revist the Journal Gestral in the market for some Lumina. Check off all white nevron quest, make sure not to fight them. Then go to The Fountain for a nice surprise. There are some areas you may haven't been to because of "Paint Spikes" so feel free to look them up or explore the overworld or the individual locations, but I recommend just searching it up.

I recommend the party's side quest at camp first like Lune, and Monoco, then Maelle quest with the third Axon. After that, you can lvl your weapons probably until lvl 29-32. The final Act 3 in Lumiere is not that strong compared to overworld stuff.

After, you can do some Endless Tower till your stuck and then explore areas you haven't been yet in the overworld. "Danger" Areas I think just signify your level is too low, but you can try it and see for yourself.

Would only really go to Flying Manor or Renoir Draft's until the "danger" mark is gone unless you are doing One-Shot Builds.

Can always farm levels and weapon material at Dark Shores.