Keep trading, you can use your profits and put it into more allies so that you can trade higher, and earn more from it. In my opinion, id never liquidate. Id always keep some level of trading going, and your choice, but any profits I made above that price I would then liquify into lands and upgrades.
By that I mean, once you have a certain level of gold in allies for trading, and you feel its sufficient, then anything made above that, can be liquified for upgrades and such.