I am trying to accumulate a very basic setup for learning studio lighting for portraits, etc. I recently purchased a used Canon Speedlite 580 EX (not the EXII) for my T1i, and now I am curious what would be compatable for slave units? I am a student and seeking something affordable. New to staged photo, so this is all foreign to me. Could someone explain what I need for a set up, or the economy way of going about learning lighting with what I have currently, and minimal additional purchases?