What are you flying, a fixed wing, quad or flying wing? You need a GPS receiver, barometer and a compass to get any data that is useable for flying.
There might be a stand-alone system that does just the compass etc on an OSD but a “simple” wing controller like the Matek F405 is fairly cheap.
Remember that flying beyond visual line of sight is illegal in many countries, as is flying above around 400ft, so check your local laws before investing.