the best "weight" you can lift is your own bodyweight! if you want a high-intensity workout that's cheap, easy, and very effective, try this....
1. sell your dumbbells to the teenager on your block for $30
2. take that $30 and buy a pullup bar -the best kind is like this one here:
http://www.sportsdirection.com/doorpulupgym.html.
3. do the following workout:
-1 set of pushups to failure (you'll be breathing reeeeal hard trust me)
-1 set of pullups to failure (ditto)
-now for the finale.... put your hands about 1 foot from a closed doorway, and kick upside-down and let your feet lean against the door....this is a "handstand". hold this for 10-15 seconds. if you can, do another one. work up to 1 set of 6 "reps"
Now, repeat this as many days per week as you can handle. It will take about a whopping 5-10 minutes per day. When you get used to 1 set, work up to 2. Then 3. etc...
Oh, did I forget legs? do 50-100 bodyweight squats per day, how? you squat down as low as you care to, then come back up. yes, they also make you breathe very hard.
when you can do 50 in a row, start working on 1 legged squats! start on stairs, or use a box to "sit" on part-way down.
Believe me, this is high-intensity. You'll get strong as hell, with no "bulk". You'll also improve your balance, flexibility, and aerobic capacity.
Keep track of your progress with a simple Excel spreadsheet, and aim to increase your workload each week.
No hype, no frills. Just results! Welcome to my current workout!