Get the Thunder TM and teach it to Jolteon OR gamble like a mad man and get the much more accurate thunderbolt (if you can't be fucked gambling it costs the equivalent of 80,000 pokedollars in coins. A lot of power and an insane speed stat makes it the best in-game Eevee outside of Espeon (which you can't get anyway). It'll learn Petal Dance whether you evolve it or not. Avoid evolving Gloom until about level 35 when it learns Moonlight. Your choice of male or female Nidoran is a choice of power vs bulk and the move Megahorn vs the move Superpower. Mega Punch really helps give it some early game power. S/he's able to learn some awesome special moves (including Surf, Shock Wave, and Water Pulse), can utilise Strength well and gets STAB Dig/Earthquake. Nidoran evolves really early and can evolve even further with a moon stone. I'd suggest Fly slave (charmander) as Fly Slaves are worse on average than surf slaves so you may as well get a good one.

Now the choice is basically Surf slave or fly slave. I'd still not recommend Bulbasaur though as his movepool's a bit wank in Gen III and you don't get Sludge Bomb until way after you beat the Champion. Bulbasaur and Squirtle make short work of them whereas Charmander has trouble. It basically comes down to how easy you want the first two gyms to be. There is a Ghost Elite four member though although she's actually a poison mono-type trainer because there was only one line of Ghost types in Gen I and Dark didn't exist so it was the only thematically similar type. Rock, Water, Electric, Grass, Poison, Psychic, Fire and Ground.

Pokemon fire red team builder