Oatmeal stout, a good way to use oats and one of my favorite beers. Smooth and dark! As for corn it can be used as an adjunct in beer to increase the amount of sugar. Look into beers called Chicha and Tesguino, if you want a all corn beer. I have yet to try these beers or make them.
On to the brew pot. If you are going to make five gallons of beer, I would look for a six or six and a half gallon pot. I like stainless steal but an enamel pot can work. A few years ago I brew pot from
https://www.blichmannengineering.com/. It was an investment and it did pay off. I do all grain brewing and getting the
water to the right temp. Then opening a valve was a big change from dumping 170 F water in to the grain. And a lot safer!