What you have to do is go through the game until you reach the first pokemon center and have finished the erand for the pokemart guy to Dr. Oak then go to the second floor to where you can trade, battle and other stuff with your friends using game boy advance link cable or wireless adapter and trade your starter to your freind for a rattata or another worthless pokemon.
Turn off the gameboy start a new game get a new starter repeat the trade until you have put 12 starters through (4 Bulbasaurs, 4 Charmanders and 4 Squirtles) then catch 6 worthless pokemon e.g. rattata and trade them for 2 bulbasaurs, 2 charmanders and 2 squirtles put yuor satrter in a computer box and you will have really easy to train nearly ultimate pokemon.