If you plan on mixing the SW
in the tank, then do that first, then after salt is dissolved, add rock then sand. Don't want undissolved salt getting stuck in the sand if you pour it on top if the sand. Also, for FOWLR
it's recommended 10-30x turnover rate, for reef it's 30-50x turnover rate. So for a 30g you'll want 300-900 turnover per hour and reef 900-1500. Use the gph
rate of all your equipment: PHs, filter, skimmer, etc. So if your filter right now is the only flow, I would tend to think you'll need at least 1 PH too. Good luck and welcome to the world if salt!!