I wouldn't consider them monsters but as a bigginer African haps or peacocks can give you a pretty good bang for your buck, they are relatively cheap and if your pond can maintain a steady temp around 78 to 82 degrees you can fit a lot on that size pond. They are colorful and a pretty interactive fish that are fun to watch. If you go that route a few syno cats will fill the catfish void.
Most Malawi cichlids are fairly hardy fish and you'll learn a lot before you invest big money and time into something like Pbass. Just make sure you understand the nitrogen cycle and how aggression works in African tanks, a 30gal is a perfect grow out as well. Sounds like you do your research so youl be fine.
Also on your pond I would highly recommend taking the time and putting a side window, a lot of good looking fish are camouflage from the top unlike goldfish so you won't be able to see much other than them feeding.
If your parents allow you to have a tank inside, you can pick up 125 gal or less on Craigslist and Facebook marketplace for cheep, I've gotten 100 gallon complete set ups for less than 150 dollars. I would start with a 120 gallon tank, you can touch into the big tank world without having to invest the time and money when something goes wrong.