If you want to keep the base combat relatively simple then just assigning # of dice based on a weapon/armor's efficacy could be a good starting point, and probably have it be like 3 or 4-sided dice to limit variance? Then you'd just roll however many # of die you're attacking/defending with and highest sum wins etc. And then add as much complexity with perks/supplementary items/friend&foe on top of that as you want
though I think limiting the variance with like a 3-sided die solves that similarly. idk exactly what the odds comparison is but I think it'd be pretty close. For example you'd have somewhere around a 33% chance to beat someone with one more die than you if you're using 3-sided