Regarding sa amount ng sand, maraming sites sa net, just search aquarium substrate calculator. Sa live rock naman, i've read 1lb/gal, so kung 75gal ang tank mo 75lb ang need mo or 34kg...
Oo, getting into this hobby is expensive, so i suggest do A LOT of readings...dont be lazy, dont be spoon fed regarding sw infos...do readings for yourself and for your future pets...in this site itself, maraming infos kang makukuha...magcocorals ka pa, mas mahirap un(well, it depends kung anong corals)...
Me, myself, wla pa akong SW tank, but i've read countless/watched countless articles regarding this hobby hoping to set up a SW soon...more readings = more savingssss & less troublesss...
The key is PATIENCE....In this hobby, good things happen slow...bad things happen fast...as they say...
I suggest panuorin mo ung "reef tank guide:52 weeks of reefing" ng Bulk Reef Supply sa youtube...nd pa kumpleto...ifollow mo na lng para sa updates....
Hope those helped...