Do what I do. Buy the fresh bagged spinach. Easiest to prepare and eat, and should be really cheap where you are (A dollar a bag for me, a bag gives me two meals' worth of veggies). I put them in a huge bowl and mix a sachet of Splenda with paprika, hemp seed oil (you can use some crushed sunflower seeds, walnuts or walnut oil for variety) and apple cider vinegar as dressing. I probably go through 2 or 3 bags a day. Rinse, throw in a bowl, pour on dressing, and enjoy. I've grown to love spinach, honestly. Occassionally I'll buy some radicchio or endivces and throw them in the spinach for some variety.
Honestly speaking the best salad greens are endives, radicchio, baby mesclun greens, alfalfa and baby spinach, but that stuff tends to be too rich for my blood.