Ash is competing in the Battle Frontier while May is competing in her Pokemon contests.
Personally, I’m not as big a fan of Advanced Generation as I was of the original series. Max and May annoy me. And it doesn’t have that nostalgia the original one had. But still, it’s Pokemon. Same old, same old. New Pokemon, new people, “new” adventure, but still, the same Pokemon.
I probably don’t have to say much here. You should know by now if you like Pokemon or not. You can probably just go straight into this series (or even just this particular season) if you really wanted to. You won’t see what slight growth there is with the characters if you do, but really, you aren’t missing much.