I recommend trying it again, and trying to level up your city a bit, to get at the good shipments. It gets really fun in the end. Also, don't buy shipments that boost the explorer, since he sucks anyway. I use him as a one-time use unit. Once he dies, too bad for him. Unless you're playing the warchiefs expansion, of course, in which case the war chief gives your other units a nice boost, once you've gotten some of the better shipments.