Drop sets is a  technique used to stimulate muscles growth by taking it to the point of complete exhaustion.
To benefit from drop sets, you need to know your effective training intensity. This is the load you carry to reach muscle failure (exhaustion) between 8 to 12 reps.
If your workout load in an exercise is light enough that you can do 15, 30 or a 100 reps, you are missing the point.
To stimulate muscle growth you need to challenge your muscles through heavier loads not through increased reps.
Once you have figured out what the correct intensity is for you and in each exercise, you push yourself to the point of muscle exhaustion and then immediately (meaning without rest) reduce the weight and continue.
In a gym setting, you can easily exchange one dumbbell set with another and continue. At home, you may not have so much room to fit an entire dumbbell set.
Adjustable dumbbells are a good alternative for performing advanced bodybuilding techniques at home.