Guild Wars 2

What about traits and stuff like that? Are they important? Or I can just upgrade them to whatever I like? Or is there a build path too?

By PvE, I mean like dungeons and by WvW I mean running with zerg.

I am new to guild wars 2 and I don’t know what to build I should do for my Mesmer. I like PvE a lot in this game, but I also would like to do some WvW from time to time. Is there a build out there for a player like me? Or are the builds out there are just for straight PvE or PvP/WvW?