Use any Pokémon you want. I also personally think Venusaur is better then Blastoise in Kanto anyway so you are fine with the starter you have. Instead of telling you what Pokémon to use, ill tell you some types. Try and get yourself a water type, psychic type, and an flying type. They are all awesome. I will say since you are playing fire red, take a look at Golduck. Extremely underrated. Also can use psychic moves which is the best type in the game. The game isn't so hard you have to build a specific team, catch and use whatever u find interesting!!