Opening herald looks weak here as it acts as village until endgame, I would wait with purchase. When you are going with heralds a double masquerade, masquerade/hermit or masquerade/sage are better as you trash faster and have better economy, thats why opponent could quickly afford gold.
Also opponents hermit->madman likely results in gold which speaks for hermit
Also sage looks good in this board as it equals gold or grand-market.
First farmland looks bit dubious, probably overpaying herald by 2 would be better but it depends what was in discard pile.
A last opponents turn is a ppr land, as both of you are capable of double province a better could be buy province+duchy and do double province next turn, which depends how consistent you could do that.