Industry(?)

So ive been playing this game for 5ish years, done almost everything the games has to offer except industry, thought id give it a go afterall, got all my industry and science skills to 4 or 5 but still dont know where exactly to start, I heard its not that worth it especially due to other industrialists already profiteering off the already small margin one gets, got a stash of faction and t1 bpcs, wanted to get into invention and well building, im based in null but spend a quater or half of my time in hisec, got about 5b to burn in this new venture, taking all opinions and tips on how to get started