Keep or sell equipment?

I recently received a lvl 10 ring. Should I sell all lower level rings or is there something else I can use them for?

If you have a lvl 10 ring, you don't need the others. Selling to alliance members who don't have one is one course of action. Also,selling depends on the level of server. If the rings of lower levels are still being bought at relatively higher price than NPC, then selling them in market is the best course of action. If not, I tend to keep them as emergency resources when I might be in immediate need of cash, at that time I can NPC them.

Also just a related note - if your current ring was enhanced any you can only sell it to the NPC. In that case no need to keep it unless it was enhanced a lot for some reason and better stats than the 10! But hopefully you didn't waste stones to enhance it THAT much.

Remember that if u sell a ring on market the market takes a portion of the profit. Same goes for resources and other treasures. I usually sell my rings to npc.