I did my 500 square foot garage. I had Sherwin Williams come inspect the floor. I used their professional grade stuff, not the box stuff from Home Depot.
I did two acid washes, made sure the floor was completely dry (I ran a dehumidifier for a few days). Get the proper PPE, especially the respirator for ACID.
I did two coats (one thinned out to really sink in) then I clear coated it. I want to say I had about $700-900.
I used an Armorseal product. They let me use one of the pro accounts, so it coast me about 60% of retail.
I followed this guy. I think he had about the three part series. Take his advice, don't clean brushes, throw that crap away. Also use gloves.