I've never had a fish tank before. I started with a 5 gallon reef. I tested everyday for like 3 weeks when I first got it. Things did fluctuate a good amount back then. Now I'm 2 months in and I test like once a week. Haven't had any problems so far. If you are dead set on a small tank, just go buy a standard 5 gallon tank. Your filtration is rock or sand so you won't necessarily need a fancy set up. As for lights, nothing will be reef ready. You will have to buy that separate anyways. So you will need:
Tank- Petco is doing there 1gallon=$1 sale right now
Heater 50-100w maybe, just look around
Power head - I have the Hydor nano Koralia 240
Light- I recommend a par 38
Then just rock.
Just FYI though, I'm only 2 months in and my tank is full. I have no more room for coral. I'm already considering a 55 gal within this next week. Not to mention you shouldn't do any fish in a 5 gallon. Maybe can get away with a panda. Just food for thought.