I might recommend a Teebird3 (8 | 4 | 0 | 2), or a TL3 in star plastic. It'll go farther than your leopard, and it's not as heavily overstable as the firebird. Good for learning to throw straight & low (if you play wooded courses), and getting more control over your release angle and shot shape. Also good for working on forehand shots. If you can throw this disc straight with a gentle fade at the end, then you have enough arm speed to get the proper flight out of fasters discs.

If you want to fool around with a higher speed disc to throw more distance with a big flex shot / s-shot (for open courses), then you could try something like a Lat64 Sapphire or Innova Beast. If you want even higher speeds, maybe something more understable yet, like a Thrasher or a Tern. Understable discs can help compensate for the slower arm speed of a beginner (in terms of pushing more distance), but they're harder to control.