ToME: the Tales of Maj'Eyal

Yeah so i bought this game in the past week, I'm at 40hrs and counting with 15/1386 achievements on steam. I haven't gone full rogue yet but i'm looking forward to it.

I found a stronger version of an inscription that i have active, How do i swap them? I've googled this but only find guides about how useful different inscriptions are and not how to use or manage them. Also, should i just sell my gems or will i need them for anything, i'm a thalore archer? Thank you!