Look for used PowerBlocks, or the knock off of them. You'll easily spend $100 to buy a pair of 5lbs, 10lbs, 15lbs, 20lbs and 25lbs DB's.
and you'll still need something heavier for bench pressing, squats, deadlifts, etc.
not to mention that the above weights end up putting 150 lbs of weight on your floor, vs. two adjustable powerblock stacks that only weigh 80lbs total, but give you configurations of 5lbs to 40lbs in either 5 or 2.5lb incrememnts depending on which series you get.