1. To achieve stability, the water should be tested daily until you figure out the consumption rate of cacium, alkalinity,magnesium, then dose overtime the amount being consumed. Then tested weekly to adjust the dosing amounts. Consumption wil increase as corals grow. There are alot of calculators online to figure out how much to dose. Dosing pumps and a controller are a big plus, but not necessary, imo. I use a gravity drip and it works for me. Also you will have to make up for evaporation to maintain salinity.
2. As far as adding sps to a new tank, you will get different answers on this. Some say as soon as the water tests are good, you can add, others say you will have to wait a minimum of 6 months for the tank to mature. IMO I would wait at least a month after the cycle has finished.
3. IMO I would only add a few at a time. It is easier to adjust for dosing. Everytime you add corals, the consumtion rate of Alk and CA increase. COrals add very little to the bio-load of the tank, so technically, you could add as many as you want, but that makes it tough to figure for dosing.
4. Necessary equipment would include a high quality skimmer, good lighting(led, t5, or metal halide), some sort of dosing system, Test kits for alkalinity, calcium, magnesium, phosphate, and nitrates, Powerheads for circulation. Refractometer for testing salinity.