Need advice growing

I'm new to growing and could use a few pointers and tips. I recently started my first grow indoors using MG Organic Choice- it was the only type I could find short notice (I didn't think my seeds would actually germinate) and so far it's doing its job. I'm on day 2 after planting and I'm pretty surprised with the progress. One of my questions is if I should let my plant use the same soil when I start my flowering stage or if I should change it out when I transplant? Also, is one 20W desk lamp enough? It was all I could get ahold of mostly because I live in a really small town and have to drive an hour or more to get to things I need for this grow- if not, I would probably have to order online. Also what nutes do you recommend? Pics to follow