I'd rather not either, but if we are to have something like magic then my general rule and desire on it is that it's very limited. All to often it feels when magic comes into play it's something that's like a ready-use nuclear bomb.

In an RP I ran similar to this I allowed magic, but on the pretense that as a whole it's very unwieldy and often requires an offering equal too or greater than the effect. Simple parlor tricks might be something that'd only cost a little bit of one's personal stamina like running a mile. But grander spells require grander sacrifice. In the case of the faction I played for that RP a former king utilized a powerful spell to subjugate a rival kingdom and curse it. As a lasting effect however he died of having ordered the spell cast, as well as the casters, his castle, and most of his holding. The target as well never really fully recovered and was struck with lingering damages to its health and agriculture and became too weak to be anything but a vassal to the greater kingdom.

As a result the man who used it lost everything to greater his crown and his keep became haunted. As a whole it was abandoned as the capital and people never spoke of him in a positive light.

In order for magic to be, well, "Magic" and not nearly as much as an abusive trope for someone to fall on all too easily I've been a fan of the idea that it's rare and requires immense input for effect. If someone wants to see a kingdom burn, he must in turn sacrifice his own kingdom. If someone wants to see someone die, he may have to offer two to die as well. The spirits or dieties to magic often being considerably demanding.

Gunpowder I can be more receptive towards given its known and pointed weaknesses. Though it's probably good to note that its invention was not actually for war, but a byproduct on the quest to long life. For something as "big" as that for people of a historical scope it feels too easy for gunpowder to have been developed just for war and not for something more plebian and has in its use that as its major focus (fireworks for instances, or even chasing away foul beasts or spirits which the Chinese used it for).