I have played againts HB before, and i think it is better to farm either lvl3 or FG.
Gold gain from HB is nothing special, and i win like 20 game and often dont spin an upped card.
From lvl 3 u can easily get rare and EM(about 40 gold) and from FG u can get everything, and u can win more than 30% of the games if u have good deck.