Air/Fuel - These are only accurate if they come with a wideband O2 sensor (or if your car is fitted with one from factory) and even then, it's good information to know, but not much use unless you can adjust it (AFR).
Boost - You're NA right? So you're not going to see any boost.
Oil Pressure - Could be useful
Oil Temperature - Not so useful
Tachometer - What's wrong with the factory one? unless you are exceeding it, it's in the best position to see anyway.
Vacuum - This will range from ~20-110kpa (or whatever units) will not provide any useful information.
Volt - Could be useful if you're running alot of battery sucking accessories, or like to leave your stereo on for long periods, or go to alot of drive-in movies.
Water Temperature - Could be useful, if you don't already have a factory one fitted.
I guess it depends if you want the gauge to serve a purpose and display useful information, of just fill a spot and look good. If it's the latter, just get the cheapest one with the most flashing lights.