DO NOT put a gar in there - in a short period of time you'll likely have a grand total of one fish in the pond, i.e. the gar. They are voracious feeders and commonly grow to 3 and 4 feet. It would eat every last fish in the pond, likely including any bass you add. Correct me if I'm wrong, any biologists out there, but that's my understanding of that particular species.

The fish with a larger mouth was likely a pure green sunfish, as their mouths are typically almost as large proportionally as LMB.

Getting bass in there is priority one, more important initially even than feeding them as not much growth is going to occur if they're badly overcrowded, which judging from your pics they are. You only need ten or so bass, and that's allowing for mortality of a couple bass. Once you have the bass in there, if you feed daily, within a few months you should have some eaters in there, and in a year or two some decent-sized ones.