For a ceramic coating, you'll need to apply to clean, bare paint. Once the coating has cured, you can wax on top but by doing so you're basically wasting wax because it won't bond to the coating.
AG Ceramic Spray is more sealant than coating though. Ideally, apply it to bare paint and wax on top - it still won't bond particualrly well, but AG Ceramic Spray has poor durability for a ceramic itself so you'll need to top it up every couple of months - there are a good few waxes that will give better durability, in all honesty. If you wax on top of AG Cermic Spray regularly (probably needs fortnightly top ups at least) it should extend that a bit... maybe three or four weeks at a push.
Always wax on top of any sealant/coating, not under, for best results.