I'm confused - when could White have played b4-b5 in this game and not just simply lost a pawn? Also, if Black had allowed b4-b5 by not playing a7-a6, what would a pawn on b5 accomplish for White? It's not exactly cramping Black very much and in fact will require at some point a third move (probably a3-a4) for protection.
I don't know WHEN it might be played, but to me b5 would have been fine for Gilded's 19th move, and Raf8 would have been as well.
I just finished this game, again trying not to play c4 since everyone says that beginners should focus on the main lines. I have yet to annotate the game and again I felt my opponent didnt take me seriously, most importantly where he left his bishop hanging. Not saying I should be taken seriously lol but more that I feel it hurts my learning experience.