The LEGO top exhibitions I put on are similar to what you have in mind. Since the tables are usually supplied by the venue, I find myself contending with spinning surfaces of variable smoothness, friction, and color. And some tables wobble or slope.
So I bring my own spinning surfaces and leveling shims. A cloth table cover with a fine weave goes a long way, as it gently suppresses travel with surprisingly little friction. Since most of my tops show best against a black background, I use cheap black bedsheets.
I also bring a concave, low-friction arena akin to the bamboo bowl johnm showed. This is essential for battle tops but also helps to contain tops that tend to launch with high travel speeds. The large plastic "top bowl" Christian sells is excellent. Most concave mirrors and lenses are much too small for this purpose.
For most tops, however, I prefer a flat, low-friction arena with a very low lip. Glass microwave oven platters fill the bill nicely and are relatively inexpensive on Amazon. You can see my go-to platter in the video I posted above.