There’s not really a strict equipment requirement when it comes to pixel art. With that said, judging by the work you have posted currently I would recommend that you not attempt to sell your work for a while–you need to develop your art fundamentals, and trying to build products to sell at the same time is going to cut into that.
After all, if an asset can be made without a significant time investment or existing skills then most people won’t need to buy it–they could just make it themselves.