The amount of weight I use (and anyone) depends entirely on the workout. There are some workouts and exercises, like Jari Love's shoulder work, where I will use 3#. Others, like P90X lat rows, where I can use 35#.
I have weights that range from 2# (for shoulder rehab work and some functional workouts) to one 35# dumbell (for 1-arm lat rows, so I don't need a second one!).
I hope you don't fall into the trap of thinking, "Wow, X, Y and Z use ### pounds, so I should too" or get discouraged because you are using less weigh than others.
It takes time to work up to the 'big weights' and you will gradually buy more weights as you need them (like I had to get my 35# weight when I got into P90X). At the very beginning of my home workout training, I just had a set of Heavy hands that I could adjust from 1 to 3 to 5#. Then I added weights to get to 7#, then 10#....