Pokemon yellow is the only pokemon game that is like the the Pokemon Tv Show. You start with Pikachu, it does not like to get into the pokeball so it will follow you from the back. Check it mood by talking to him, it is quite cute.
New pokemon ?
There is not new pokemons in pokemon yellow but the amount of pokemon is difference form pokemon red.
what differences ?
The pikachu you have will not evoloves in Raichu and i also can't find any pikachu at power plant.
Caterpie is so common is Yellow that you can't find any weedle.
It will be much tough to fight the gym as you start will pikachu. You can get Charmander, Squirtle and Bulbasaur from policeman and town people but they are onle at level 10.