If you are building an arena then you need to be sure you get it right.
For what it costs I would have the area trenched to about 2 feet, trenches about 8 feet apart, doesn't matter if they go long ways or across as long as they go to the outside of the arena and fill these with a smallish stone. This will drain if necessary. On top put your gravel, roll it well and then put in a membrane. This stops weeds growing up through and the stone from coming up through the sand.
Then put on the rubber and if you want a surface that doesn't move get rubber strips rather than granules. These strips that we get in the UK are from car surrounds and are anything from 2" - 6" in length. They hardly move at all even with lungeing. Makes maintenance negligible.
Chains dragged over if fine but if the surface moves then the only way to get it off the sides without spending a fortune on a machine, os with a shovel.