Basically will repeat what has been said.
Get a tank is the first step
For filtration we generally use live rock for all biological filtration and a skimmer for mechanical filtration.
Light is very important for corals and some require more light than others. In very oversimplified terms you need less lighting for things like zooanthids and soft corals, lore for LPS and lots for SPS especially acropora. Look into T5 or metal halide lighting if keeping things on the higher lighting requirements.
Flow is also very important, look into the propeller style powerheads as they are very efficient and can move lots of water. This is another area where a lot of new people thing they have plenty and could really use a lot more. Again here SPS will benefit from much more flow.
Water, most people will use a RO/DI filter to purify their water before they add salt. There can be some pretty nasty stuff in tap water and you take a chance using it. You could be fine for years and then one day the flush the hydrants down the street and the disolved materials in the water skyrocket causing problems or killing things at worst.
Test kits are really important to track trends. I would recommend at the least in order I feel their importance with the first 3 being critical is salinity (refractometer), temperature (good and proper heaters), alkalinity, and I would also do calcium and magnesium as they can have an impact ion alkalinity. Lastly a nice to know is pH and that will fluctuate with lights on/off as photosynthesis occurs. As longs as alkalinity is in line then pH is normally ok.
Lastly lots of patience as things take time to cycle and get some stability.
Welcome to the club!
