Which magic schools should I choose for the late game? Or should I go for a specific artifact?

I've been reading here, and everyone is so detailed about hero builds, saying to take spellcasting, education, and summoning. Okay. I leveled up 11 times, and summoning never appeared... :( How is that possible? A 15% chance, but instead, light magic keeps appearing, several levels in a row... And what happens is, by the time you level up summoning with this setup, an opponent will come and defeat you easily. And you've basically lost with your Hafiz, gremlins (I don't understand where you see their super-mega damage, even if you consider the bonus from the hero, what's the point?), the only good thing is that the ballista shoots strongly, and that's it. In the Mage Guild, some useless spells like "Sorrow" and "Wasp Swarm" appeared. Has anyone ever used Wasp Swarm? Is there any effect? (
Anyway, I'll try playing again.