You're one of my favorite creators on this site, and I just wanna say I love this game. The controls are pretty good, the final boss is hard but not hard enough to put you off the game, and the limited amount of spells are all pretty cool. Anyway, im gonna put some tips here.
Tip 1: Build your "deck" around a specific weapon type, such as orbital, and frost. Upgrade your chosen weapon type and choose mainly that kind of weapon, along with frost, since most frost spells are just better than the flame ones
Tip 2: Use the dodgeroll ALOT, especially when fighting the final boss's second phase.
HOW TO BEAT THE BOSS
During the attack when he flies aboce you, just run from one side to the one side of the arena to the other whilst dodgung. When he comes down jump over the wave and attack him, he's really vulnerable there.
When he starts smashing into the walls, dodge him and be wary of the projectiles spawned when he hits the wall (during the second phase you want to spam dodge roll during this attack since it causes his orbitals to shoot way faster)
When he goes into the middle and spews out projectiles, go under one of the platforms as they will block the projectiles.