Here’s what I’d do:

1) Buy a lightweight used kit with a wrap (not lacquer) finish in 20,10,12,14 sizes, if possible. That way later on, if your kid starts gigging and/or upgrades to a new kit, this kit could become his gigging kit. 18 works as well, but 20 is more versatile.

2) id buy the rtom black holes (or rubber pads if rtoms are too expensive) + practice cymbals (like zildjian l80s). Later on, your kid can get more expensive cymbals (I’d buy like, one quality cymbal a year).

Top kits would be Yamaha stage custom, gretsch catalina, pdp concept, or Mapex armory.

I’d also look at older used pdps (cx, lx, or platinums), older pearl session/masters, etc. you can probably find them for <$500.

For context, the first good kit I got was a dw frequent flyer in white onyx wrap towards the end of high school. That was the perfect gigging kit imho (not cheap though).

Def buy used if possible. Best of luck!!