No onion, oil or vinegar in NY style sauce.
The most important aspect is that your tomatoes should taste good right out of the can. 6 in 1 have a good rep, so they should serve you well. I've tried 4 different brands of SMs and all of them were tasteless/watery for 4 minute bakes, so I'd nix the SMs for NY style. I'm not sure how places like L&B Spumoni gardens get a flavorful SM with a long bake, but I have heard stories of cooking the tomatoes beforehand- so that could be it.
California tomatoes generally are pretty tart, so, for NY sauce, you're almost always going to want to add some sugar. The trick is to add enough sugar so that you balance the tartness, but not so much that the tartness completely disappears and the sauce goes dull. Salt is also a key player, even if the tomatoes are packed with some salt. It's important to keep in mind that the cheese (and toppings like pepperoni) brings a lot of salt into the picture, so the sauce should be a bit undersalted to compensate. California tomatoes, sugar and salt is the most basic sauce you can get, and with the right tomatoes and the right proportions, can be sublime. Beyond that, there's oregano, of course. Some places will add the oregano as topping, while others will add it to the sauce. I prefer in the sauce, as it gets distributed more evenly. Garlic can be added, either in a powdered or fresh form. I prefer fresh, but I keep it to a bare minimum. Dried basil has no place in cooking, period, but a little fresh basil helps a sauce.
That's it. Play around with those ingredients. You'll know very quickly if you've added too much oregano, garlic or fresh basil as their flavors are incredibly distinct.