I like much cardinal, I like the choice
Ok now to answer the question. If you want a tang there are only a few that could work in a tank as small as 75 gallons. If you really want a specific tang you may need a larger tank.
You should have about 1-1.5 pounds of live rock per gallon. Unless you want just a glass bottom research your planned livestock and see if any require a deep sand bed, like jaw fish for example. I would avoid using crushed coral in your sand bed.
For filtration the live rock will do a majority of the work for you. I suggest a sump tank with a protein skimmer.
Lighting is rather easy for a fowlr
tank. But if you plan on having coral or anemones in the future I recommend starting out with quality lighting such as leds.
As for money, salt water is a never ending money pit.
Its worth it thought.