Try to do this 6 exercise double dumbbell workout as quickly as possible while maintaining good form if possible try to use the same weight for all exercises, and don't put the weight down until the whole circuit is complete, perform the circuit 4x's resting a minute or two between sets.
We love these adjustable dumbbells from Rep Fitness. They take up very little space and are also very durable compared to other adjustable dumbbells on the market.