In my start of saltwater, I started out with a few damsels. at the most they are $5. that help boost my confidence when they didn't die on me
having a QT tank is paramount. I have a 5 gallon as qt right now and it's done its job. when my clownfish was sick, i was able to nurse him back to health. it will be a heartbreaker to lose a salt fish, on average the price of one starts at $20
And yes, bigger is better. alot of the salties require a bigger tank, most of the interesting ones anyway. i've seen some tanks as small as 10 gallons, but it only had like 1 fish in it with a shrimp.
i stayed away from the SW
idea for years and broke down my mbuna tank and went with it. I'm so glad I did!