Advanced Nutrients and General Hydroponics are well known, widely used nutes. Check out B.C. Grow nutes, if you're looking for something rather cheap. My whole kit cost like 20 bucks for everything (grow, bloom, micro, extra flowering nutes, generic superthrive, rooting hormones, etcs)....
i say natural meaning organic will be the best you can go. here's a simple organic mix, 2 cubic feet of compost, 2 cups each of bone, blood meal, dehydrated manure, kelp and lime. you can use an organic tea of guanos or kelp for flowering.