5.2 is garbage according to many here. I used it for my first dozen or so all-grain batches, but moved to Bru'n Water and salts after that.
Common salts are Gypsum, Calcium Chloride, Epsom Salt, Baking Soda, Non-iodized Table/Canning Salt, Pickling Lime, Lactic and Phosphoric Acid. There are others, but those are most common in my experience.
I but most by the pound from MoreBeer and pack in mason jars. The exception is Epsom Salt, that is from the local CVS/Rite aid. They are all cheap even in small quantities. Maybe $1 per ounce, and $4 per lb.