or you could save all of the $70 until you get more money then find a nice used 55 set up for cheap on craigslist or MFK and set that one up nice. but if thats not an option get the sand and save the rest for a stand for your current tank.
and I concur....get a used tank from craigslist. best investment you can make. you could easily get a 55g tank with that money, just gotta look around...