For lights, it really depends on what you want to grow. Acros, clams etc will need a lot of light (8 bulbs+ etc). If you're unsure and if you can afford it, i'd say get lights that can support anything you may want (250w metal halides, 8bulb+ T5 fixture, LEDs etc).
As for buffers and chemicals, I'd stay away from them for now. No need to add anything if nothing's wrong. Test your water and make changes as you go etc.