There isn't really much for you to do at all in Mahogany Town as a matter of fact. The Gym is — of course — blocked by someone who's not going to budge for a bit.
There's also a tree with some antenna thing sticking out of it. Hmmm... The shop inside sells a bunch of suspicious items, too. Weird!
Anyway, not much else for you to do here except head north, since the guy to the town's east is blocking your path and trying to sell you a RageCandyBar for $300. Whether you buy it or not (it's a key item now so it isn't like the original game), you won't be allowed to pass. So get moving to the north to Route 43!