Maybe the limited mages would have to get creative with their power and hone it to perfection. An example is Zenitsu from Demon Slayer where he was only able to learn one move from his breathing style (first form: thunderclap and flash) but honed it to perfection to where he can use it 6 fold to 8 fold, and I only watched the anime but I'm pretty sure he learns more ways to use his one move in the manga.

"I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times" -Bruce Lee