Just follow my simple Advice above, Rael!
This is a Real wonderful Opening, where Black doesn't have a clue, what is going on here, and how fast they will crush own fine position! This is a Fun, because this is an Open Fight, out of books, where you can realise your Attacking Skills, not a Memory...
b5 not worked well at my games here...
But the Queen at d6 blocked own Bishop on f8 for better places to stay active.
So, a3, protecting Pawn b4 at that case is OK, because it put a Black Queen at Question, about a future safe escape from d6...