Bro welcome to the world of reefing. Me not an expert just a reefer for a long time. Let me try to help and I'm sure lots of friendly bros here will chip in.
You can get natural sea water, sand and liverocks from LFS try those in Pasir Ris farms.
Let yor tank run for about 3 weeks empty then slowly add livestocks.
Lights can be simple LEDs or tubes if y plan to keep easy corals like mushrooms and zoas. And some fishes. Lot of readif materials in the forums. Good luck