Depends somewhat on the material. Our arena is dirt - black dirt with clay. I use a row cultivator to break it up about 4" down and behind that I pull a section of an old spike drag harrow to break up the clods and level it out. Does a great job and it's cheap. I usually make 1 or 2 passes and it's good to go.
If you're talking sand, there are some expensive ones available like the TR3, arena ripper, and more. You could fab a facsimile of one of those.
One of our neighbors has a really nice King Kutter pulverizer - basically it's got two rows of spikes followed by 2 spiked drum rollers. Leaves a great surface.
The really simple approach would be to fashion a drag with spikes on it, but in my case, I needed it to go down deeper.
LAXPatrick