I didn't have Yellow, but my cousin did. She got stuck on the first gym, and asked me to help. This was years after she got the game; I'd read about using Butterfree on the internet. I tried that, but it was hard. I don't rember exactly how I did it; there was no special strategy. It was a team effort which required every Pokemon. Pikachu wound up bearing the brunt of the attack simply becaust it had more hit-points. I had to buy poitions, if I remember correctly.
Later I got a copy of Yellow, but it wouldn't save. Once I got as far as Mt. Moon; I got past Brock using the same desperate methods.
† I am a Christian and proud of it! Copy and paste this into your sig if you are too.†