when you get to skill leveling, there's a guide on that too. just farm assault weapons (pride ones too if you get them as they do act like assault mostly and have high stats). quick way to get stronger is to get SSR and SR assault weapons as your damage output really jumps when those weapons get high skill levels (especially on SSR).

And you might want to start off focused towards an element (if you get a 100% eidolon, focus on that element first), then spreading out to others eventually. there's a guide on that too