You can't get ampharos in crystal -_-
(which makes me a sad panda in my crystal version D= )
Really, anything will work well for you since this is an in-game team. Really all you need to do is make sure you have something to beat Whitney's miltank. Chikorita's poison powder and reflect combo does well, as does a hoppip with leech seed and sleep powder. In fact, it would be good to get a hoppip just for that reason. It learns sleep powder very early, and leech seed is a great move. Even if you switch out, it'll work. Hoppip also does great in sprout tower, so you can train it there once it learns tackle (lv.10). So, besides hoppip, I'd recomend something that can learn the elemental punches and has decent special attack to use them with (read: not hitmonchan). You can buy the punches early on, and they give you great coverage. Abra is perfect for this, and you can find them right outside of Goldenrod, which is where you'll be buying the punches in the first place. Totodile would probably be the best starter, since it doesn't get a type disadvantage early on, and you'll have a hoppip anyways. (Although its easy enough to beat Bugsy and Falkner with a chikorita as long as it has reflect and poison powder). So, a team of:
Totodile
Hoppip
Abra
Physical Attacker
Fly
HM slave
would work well. Of course, you can do whatever you want, these are just some suggestions.
