The basic equipment you need is lighting, a heater, something to move the water, and some rock to perform biological filtration. From those basics, you can get more elaborate and complicated, but the basics are lighting, water movement, and live rock. If you have more specific questions, what specifically you want to keep, what your budget is, etc, we can offer more help, but the question you asked is so vague that its nearly impossible to answer (at least in a format such as this).
Oh, and obviously you’ll need a refractometer (avoid the swing arm hydrometer).