Miltank is actually really good in-game in GSC. I used it in my first run through.
I like shiny, but go with what Alice says. Alice knows cutesy things better than I do because she is a girl and Lilligant is her favorite. I don't want you to be confused just because I have a different preference.
I used Typhlosion, Miltank, Pidgeot, Gyarados, Tyranitar, and Dragonite when I was 8 years old. You don't need Pidgeot. You also don't get Tyranitar and Dragonite until very late game. Red Gyarados is also very cliche, so you could try...
Starter | Ampharos | Miltank | hm slave | Slowbro if your starter isn't water. | One other pokemon.