Herbalist is a really bad opening here. Herbalist is strictly worse than a Copper if you don't use the treasure top-decking or the +Buy, and since you opened Caravan you have no treasures worth top-decking. If you had opened Silver/Caravan, you would have hit 4/4 rather than 4/3 on turns 3 and 4.
So, a couple of things snowballed:
1) Your Herbalist open ended up weakening your first reshuffle, which has a spillover effect for the rest of the game. You pretty much lost a shuffle of tempo there.
2) This deficiency was emphasized by your Caravan missing the reshuffle, which put you far behind.
Strategically, realize that hitting $5 is really important in this game. Rabble is your draw and Cities are your village. Key $5 cards generally mean that +Buy is less important than building economy until late in the game, because hitting $10 is really hard. Since you will probably want a Lighthouse or two to protect against Rabble/Sab, that's a (non-terminal) Copper in your deck. Adding another (terminal) Copper makes it very hard to cycle your deck and get from $5 to $6/$8.