with proper form and enough repitition, you will get benefits from 2-3 pound weights. I use two pounders, and they definitely work. Target has some great 2 & 3 lb. ones for like $2.50 each or something.
I have found a big difference in my body's tolerance to cheating and the shape my body is taking due to weight training. It is hard work but I think the results are so well worth it! I bet you will look amazing in your bridemaid's dress!
in my aerobics class we used 12 oz drink bottles and filled it with sand or dirt. its cheap if u don't want to spend much money but weights at walmart aren't very expensive...since you say you do a lot of cardio..try holding the weights in ur hands while u are walking or running...u can start off with 2 1/2 lbs or whatever is comfortable for you and work ur way up...