The truth is you can actually get a great workout in with only one dumbbell.
Head out to a sporting goods store and buy a dumbbell that will be challenging for dumbbell rows ( challenging but, not the heaviest you could use, think 80%) and then do the following
Goblet Split Squat x10 ea leg
Pushup x10-20 ( no dumbbell needed)
1 Leg Straight Leg Deadlift x10 ea leg ( dumbbell in hand)
DB Row x10
Do this circuit 3-4 times and you will have a great total body workout with only one dumbbell.