You can only have 1 +Str effect, even if 3 items are equipped. Dumb, yes, I agree.
Your rings aren't bad, but the angel +6 is better and more dmg. Angel necklace vs frint soul is kind of a wash. No real difference.
I would look at investing in other things that can boost dmg cheaply. Some agathions or low enchsnt artifacts. The angel ring will be nice, but you may get better bang for your buck on other items.
Focus on skill power, p atk. Crit dmg, p skill crit dmg, patk.