I'm a later bloomer, and what helped me was going to places where close to 100% of the guys were gay. Hopefully there are some places like that in Corpus, or in other places you might spend time, like SAT where I used to live.
I know the gay bar & club scene doesn't appeal to everyone, but you don't have to drink. And maybe you can go with friends, to avoid feeling awkward, and getting hit on more than you'd like. Perhaps you know of other places & events where the crowd is largely gay. Check online gay resources to find them.
Then simply study the other guys, and learn for yourself. Over time you'll just naturally assimilate what the gay look & mannerism are all about, upon which I believe gaydar is based.
Not that you'll have seen a complete sample of all gay guys, cause many don't frequent the bars & clubs, or go out much at all, and others are so ungay in their ways they wouldn't register on anyone's gaydar.
But if you want to hone your gaydar skills, that's one way.