I have a ring of wielding(+20% one-handed damage) and enchanted daedric gauntlets(+18% one-handed damage).So I was wondering,will these 2 bonuses stack,giving me +38% one-handed damage?

Yes, they stack. My gloves/boots/necklace/ring all give me +47% one-handed damage each, which stacks to 188% + the 100% extra damage from the skill tree stacks too. 288%

Easy way to tell. Just equip it one at a time.(usually multiple bonus slots do indeed stack,this game is meant for you to get crazy high)
You can get +100% from perks ...that does stack with the item bonus.