I think making the Other Realms fit the themes of your game is a good start. If you're doing Anglo Saxons vs. druids then maybe fitting it to the celtic pantheon could be cool. Think of realms like domains or schools of magic in 5e if it helps,
Otherwise, if it's the improvised magic or the connection to hit dice that isn't landing for you, the system from which it's derived is worth a look:
https://slightadjustments.blogspot.com/p/glog-magic-dice-primer.html
The system was the invention of Arnold Kemp but I think Spwack's version (above) is pretty neat.
But I may have gone off the rails a bit there. Is there anything specific I can help you with?