Hydroponic Nutes basics?

Does anyone have abasic guide to where to begin with hydroponic nutes, how do you pick them, and if NPK is all that is needed, how do you pick what ratio, would I only need to go out and find the cheapest one, etc etc.

There should be a guide on this and a sticky to it

i have a great botanicare recipe and guide in my thread, my 3 stages of flower.