sand is pretty good to use as its what they have in their natural habitat. but dont use it from the beach as it contains salt but more importantly it contains heaps of organisiums so when u fill ur tank even after extensive cleaning they will fowl the water. the cheapest and best way is to go to a hardware place where u can buy sand in 20kg bags for about 7-10$ aud. clean this, repeatedly and use this.
Use store bought sand as stated...but put a layer of crushed coral under it.That way your ph stays bumped up and you don't have to mess with chemicals to do it.
Home Depo (as far as I know from trading spaces you have them down there) Silica Sand it nice and white (as long as your do a very very good job rinsing it which prevents your water from getting cloudly)
If you really want a maintainance free system you can start with some egg Crate (white platic Grid) and fill the holes with elemental sulfur (Pea sized balls of it) . Then place some fiber glass screening or Spun bound landscapeing fabric over that and about an inch of crushed coral and 1-3 inches of sand ontp of the coral. Anerobic bacteria will utilise the sulfur in breaking down the nitrates that build up and the coral will keep the ph High. However I would suggest Rigorus water testing and maybe a test run for a few months with some guppies or something (I just finnished seting a reactor up that involved elemental sulfur hasn't started working yet but its only been going a few days)
Edit: Said Coral would lower PH meant it would raise it.
Opcn Made a typo ) Crucshed Coral will raise your pH to about 8.2. The reason I brought up the Sulfur is that its a really cool way to bring down the maintainance on a tank but it can only be done is systems that need high pH such as african Cichlid or salt water