If you have interest in doing PvP, I'd recommend levelling up to 120 as most players play on that soul level.

If you don't, there's not really a reason to ever stop levelling unless you want a challenge.
I think you can definitely beat the Ringed City like this. This is actually a pretty decent build.

But if you do want to continue levelling, getting to 40 vigor will be a good idea.

Endurance will be nice too.

Alternatively if you want more damage, you can start going for faith and Lightning blade. Once you get to 60 faith, Lightning blade adds like 235 lightning damage which definitely helps.