Yes, with frozen veggies, you can use as much or as little as you like, which is an advantage. Some brands of things like frozen spinach are packaged in cubes, and they're easy to use. This is an example, but probably you (and I) have less expensive alternatively:
Oh, and you should also get some kind of insulated bag to carry them home from the supermarket. If you drive to the market, get a cheap styrofoam cooler to put in your trunk.