You don't need to buy those soil components seperately, they are generally what's in a generic potting soil. The soil I got was from a local garden store, and it was their brand. I just added more perlite to it, so the perlite amount was almost 50% of the mix.

As for light, it sort of depends on your preference. Some people keep their seedlings at 24 hr light for the first month or so, but others have the light on 18/6 right away. I had my plants under 24hr light for like 2 months, but now ive switched them to 18/6. So it's up to you.