I am new to the game and have been hearing and reading a lot about how many core sets I need or should buy. My question is this. Is there a way to obtain singles from perhaps FFG? I mean I can't be the only guy to have thought I'd like extra cards but don't really wanna buy 2 or 3 core sets?

It's worth buying a second core set for the cards you only get one or two of in each set. It's probably not worth buying a third. You'll only get about 10 cards and you probably won't want more than two of them in a deck anyway since they're unique.

There's no way to buy singles (except from other players).

Covenant TCG sells singles, but it's primarly neutral cards like Sure Gamble and Melange Mining Corp, many of which you get three of per core set anyway. I guess if you made multiple decks that needed these it would make sense to buy (maybe, though it might end up being cheaper to just buy another core set).

Getting another core set should provide you enough of the singletons to put together competitive decks, as pointed out above. But it also lets you build more than one Corp and Runner deck; I find that to be useful, as it allows me to have "standard" Corp and Runner decks I can use to test my experimental decks against without having to dismantle every time I want to build a new deck.