- If I remember correctly, devils and dragons are probably the better of the races. However, to get the good monsters, you have to breed like crazy. Basically, save before you go on a breeding session to see what is going to be created, because if you don't like it, you'll definitely want to reload. Almost all of the best monsters in the game can only be obtained through breeding. You're also going to want to plan ahead. Breed a monster just so you have it and can breed with it later.
- It also helps (just like in the original pokemon) if you have another gameboy to trade with. You can get some pretty good monsters easily by trading with someone else. I doubt that's much of an option nowadays though, not like it really was back then either.