Doesn't have to be cumbersome at all. Plenty of possibilities, but a few simple limits can easily make for a good game. Set a number of levels (at least 10 to really make a difference), to be spent on the wizard, limiting stat increases and spell casting value decreases to 2 probably (new spells don't seem necessary). Gold depends a bit on whether you want a mix of cheap and better troops, or mostly elites. I personally like the idea of 1000-1500 gold to be spent on both soldiers and magic items, which allows for some or quite a bunch of magical gear depending on the soldiers picked.