About my horseback riding arena?

Okay, I have this arena kind of. Like, it used to be a pasture, but it's flat and in a rectangle shape so we started working it up last year and now there's no more gr. It's a little small because the one side has like a frickin rocky mountain and we had a guy come look at it and he said we'd have to use dynamite, but anyway. When we work it up, the ground is fine, it has some rocks that we always have to pick out, but it's still okay. But if it rains, it's super muddy for like 4 days, and then after not working up it gets really hard. We were gonna put sand in it, but do you think if we keep working it up like twice a week and picking out rocks, it will eventually be okay?