You need: reef-capable light; decent skimmer if you want stony; nitrates way, way down to 2 or thereabouts---do this with water changes and maybe vinegar dosing if an older fish-only; and if you're going stony coral, you need to track not only alkalinity, but also calcium and magnesium. Proper levels are easy to maintain if you put calcium powder (kalk) in your topoff water. I don't have a controller, and have no trouble maintaining a reef with a fair fish load while out of town for a month.
You need to have no fish that eat corals, or you need some real fast-growing softies that can keep up with them. It's a general rule that if it grows that fast its inedible by most things.
Softies are not as fussy about light or skimming, but they can take a tank very rapidly: two purple mushrooms on a big rock can cover it entirely in months, and in real reef conditions things like green star polyp can crawl right up your tank glass.
The keys to a reef are proper lighting and water quality. The good news is that your fish will be extremely happy with that water.
Honestly, I find a fish-only incredibly hard compared to a reef. My corals tell me at a glance whether the water quality is 'on' or not, and if they're extended and happy, I know the water's ok. Fish just look at you and deny anything's wrong until they're desperate.