I love redundancy. I dive with two computers. One is air integrated. I also have an analog gauge. Whether you go air integrated or purchase a gauge first depends on your personal preference. Either one is fairly reliable. (And if not, that’s why you 1) check your air pressure frequently and 2)stay near your buddy.) Also, my buddy hates hoses so her computer is air integrated. She doesn’t use a gauge.
I have a console mounted compass that came off the pin and is useless. I prefer navigating with a wrist mounted compass anyways. In low vis I can hold the wrist mounted one right in front of my nose. It’s also easier to keep it lined up in front of me and makes my navigation more accurate.
Don’t sweat your air consumption. It will get better with experience. If you want to improve faster, work on your buoyancy, keep yourself in good shape and do yoga because it will teach you how to relax when you are under water.