We use simply the three primary colors from HydroForce:
Red
Blue
Yellow
and mix them accordingly. Yes, this is mostly for rental properties, BUT talk about a great training ground!! We're getting better. In fact, my guys are getting better than me!
I would start a simple kit with the three primary colors, with some PH stabilizer, Bleach Neutralizer, and a good Dye set. Then, when you start getting better and more confident, you can evolve into a kit or system.
If you're still looking for a system or kit to buy, I'd stay away from powder dyes and stick with the liquid dyes.
My $.02
Shawn