It depends on the LFS
. My preferred LFS
sells mainly Oceanic...but my backup sells mostly IO and Reef Crystals.
IO salt is ok, but if you want to go reef, I'd avoid it. It basically has low Calcium, but is dead on for alkalinity. Oceanic is much better balanced, and a lot of people say it mixes faster.
I got a 5gallon bucket for about $50 - that makes a little over 200gallons. It was on sale, but only 10% off.