A small reef is kind of harder to keep then lets say a 75/90 gallon d/t swings in Ca/Alk, nutrients, specific gravity, and such...but it is not as hard as you think. You just have to drop a lot of money because having really good gear/equipment assists in quality of life. For instance getting a auto water top off like a spectrapure ultra precise helps mitigate the swings in specific gravity, and finding a really good/effective skimmer for the tank size is a must.
You might buy another tank drill the 30 and make a sump...or get one of those pre-made overflows and sump combos. You would have to go with light livestock and should not dive into SPS coral the first thing. In my humble opinion and experience frequent water changes are the key to keeping harder corals along with Kalk dosing which is usually done through your auto water top off. Every once in a while I would dose Mg, but Kalk was pretty much the only thing I dosed. Water changes are where it's at with reefs. Which can be a PITA because of salt mixing etc. Now soft corals are really easy to keep, but are somewhat invasive and spread through tank like wild fire....stay away from polyps(especially the ugly brown ones) and mushrooms, star polyps, etc. I have found that the prettier/pricier soft corals are the slower they grow, the crappy looking ones spread like a disease.
Just remember, I did SW/Reefs for a while, but I always come back to FW because maintaining a reef is like having a diaper....it is a PITA and you have to change it all the time.
Plus tank crashes hit the wallet a little harder as well.