I think Evocation needs to change for one reason. If you get random card 9 & 10 mana, which it means you can never use it due to Evocation cost 2 mana. So change from 2 mana to 0 mana then you can use any card 9 & 10 mana. I dont think it is how it works like this, no.
Cheers
If you want to use 9 & 10 mana cards then put them in your deck…
Mage has more than enough 0 cost cards if you ask me.
Use a mana biscuit or something 
No. It’s already powerful enough and I get it played against me for 0 mana enough as it is.
Nope! If you dont have biscuit so it doesnt matter! It should be 0 mana anyway.
You make a strong argument there, 0 mana it is then. 
Or keep it at 2-mana and the spells you discover cost 2 less mana. sik up myself.