Don't get in a hurry, and buy yourself a good beginners book I recommend "Aquarium Keeping & Rescue: The Essential Saltwater Handbook & Log". It's a great guide book that teaches you the basics of what it takes to get started and be successful. Just do not follow the advice about vacuming your substrate, with a good clean up crew it's not needed. You do not want to add any fish at all until your aquarium has cycled. You also will not have that many fish in a 75. You can do a nice colorful collection though but you are trying to achieve a balanced eco-system and as such you must insure that nutrient import export factors and over crowding issues are met. If you want coral you will need good lighting either PC or Metal Halide will ensure you the best results. Budget wise PC is better but light wise Halides give you far more growth and color.
I will not start a debate on the best ways to set up a tank, instead I will tell you how I set up my tanks, which I have never had serious issues with.
You will want a good filtration system, I suggest a sump and a good skimmer.
You will require about 1500 Gph water flow in your tank. You can buy several underrated powerheads(Hydor Koralia) or one very good one(Tunze Stream 6101). Yes I know how much they are I have several and would not take anything for them. You are going to have to decide between fish or coral, remember fish and live rock will be a lot cheaper than a full blown reef tank.
Either way you will want to add about 1 to 1.5 Lbs per gallon of rock to your setup. Can be live rock or base, matters not. You can add sand at this point, I always use Caribsea Aragalive sand as it is a good clean sand to work with unlike the dry stuff which can take days to clear after adding. Do not add to much sand, just enough to come to the bottom rim of your aquarium is a good rule of thumb. Get some RO/DI water and add to your tank mix in a good grade of marine salt I use Instant Ocean but there are many others, mix to a specific gravity (SG) or 1.023.
Go to a fish mart and get a single uncooked salad shrimp and throw it in the tank. This will jump start your cycle. While the tank is cycling read your book, it will answer many questions about how to test your water and know when it's time to add animals. DO NOT ADD ANY LIVE ANIMALS until after the tank has cycled.
I suggest you start with crabs and snails at the end of the cycle period followed a week later by your first fish. Do a lot of research on the fish you want and only get ones that you know will be safe to your aquarium plans. Avoid impulse buys as well, if you see a fish or coral at your favorite Local Fish Store (LFS) ask them to hold it for you (Good LFS will do this), go home and research the animal and make sure it fits into your plans.
Next after you get up and going find a local reef club, there are many around and learn from real live experienced reef keepers. In no time you will have your dream tank. It's not hard to do a great reef tank, there are a few rules and a lot of theories. Follow that which are fact and choose which opinions and theories you want to try. There are many ways to do a reef tank right and just as many to do one wrong.
