Ok..rule of thumb when buying a tank is.....
Buy the largest that you can afford and have room for. 2 reasons why the larger tanks are better...
1. The larger the tank, the easier it is to maintain water quality.
2. Buy the tank you will be happy with for a while....nothing sucks more than buying a smaller than you really want now, and end up wanting a bigger one right away.
As far as equipment to use...this is really based on what kind of budget you have to work with. You will need these items for sure...
1. Filter system
2. Heater
3. Lighting System
4. Protein Skimmer (not a MUST have but you should have one)
That is the bare basics of what you need to start with....I did not include substrate, live rock or canopy/stand since they are variables and it all depends on your goal. To get much better advice, list what it is you want from a tank...reef, fish only, predator, etc etc.
You will find a HUGE amount of information here, there are some exceptional people here with alot of experience. To better let them help you, list what it is you want to achieve from your tank.
Hope this helps you get started