Sorry to hear the dive shop stripped you 1k for masks, fins and snorkels - they must have put every effort into selling you the most expensive models they have. (Mask - 60 bucks; fins: 100 bucks, snorkel: 20 bucks; times 3 comes to 540 bucks). But when you think about the ultra-low retention rates (5%) by which newly certified divers actually stay with it, it's no wonder that the stores do anything they can to maximize their profit off the bat. But this is only a side note and doesn't help you a bit with your question. Diving is not a cheap hobby, that's for sure. That said, I firmly believe that by starting out renting gear and shopping smartly, and most importantly, not falling for all this marketing BS but keeping it simple and real, scuba diving can be done without a bottomless wallet. My answer to your question as to what you absolutely need for your OW dives is this: none of the above. You should be able to rent everything you need from the store. Don't let them talk you into committing to buying any further equipment unless you really want to. Almost all pieces that I bought as a beginner I now wish I hadn't bought. There is simply no way of knowing what your needs will be and what you REALLY need for the diving you want to do. In the beginning, one has no idea what's out there, what kind of diving one will do and how to choose the best equipment for that. don't let the store put you into one of their "complete package uniforms", fork over a couple of thousand bucks and then be stuck with equipment you may hate or find uncomfortable or not useful for your kind of diving etc.
Remember: This is about getting to explore the underwater world and see how you like it one and foremost. All equipment considerations follow from there.