The reason that these are *not* sound is the following:
(1) Why does white play b4? It's to distract the Bc5 from controlling d4, so white can play d4 and take over the center in one move. That's the compensation for the pawn.
(2) Since white has played d3, it's now a total waste of time to even try d4, so b4 became useless, and just throws away a pawn.
However, I recommend a player of your level to play the Evan's Gambit, if you like it. It's a good opening that follows general principles and will exercise your tactical ability. Plus, it's fun to play!
My question is would you guys consider these other similar variations to be sound:
1 e4 e5, 2 Bc4 Nf6 3 d3 Bc5 4 b4
1 e4 e5, 2 Bc4 Nf6 3 d3 Nc6 4 Nf3 Bc5 5. b4