Simply create touch spell with as many symbols as possible and cast it into air. Mana wont be consumed but you will gain exp.

Can you remake exp gaining so that exp will be gained from actual mana spent casting any spell and not mana used on effect glyphs?

I noticed recently too, i'm sorry. I have a fix that should solve that (but i am unsure if it will lead to shenanigans with linger) but i also have important stuff this weeks and i have unfinished stuff indev that might cause issues if not disabled correctly so i can't solve this quickly.