The gel food is at Petco. I bought it as a last-ditch impulse item but it's worth tracking down for fish rehab--Formula 1.
I don't have great luck with mysis, although it's the go-to food for a lot of people. If you have a LFS that carries Rod's Food, get the fish eggs. They're expensive, but I've never seen a fish reject them. Once again, not a food for maintenance, but good for rehabilitation.
I keep mostly gobies, and mine get a daily blend of the following: shaved Rod's food, shaved mysis, Rod's fish eggs, rotifers, cyclops and oyster eggs. This maintains the following fish which are a combination of sand sifters and feeders from the water column: Rainford's goby, mandarin dragonet, two spot goby, yellow clown goby, y-bar goby, Hasselt's goby, flaming prawn goby, masked goby, tiger goby, plus Banggai cardinals, threadfin cardinals and even a bannerfish (butterflyfish). Something for everyone.