I'm going to spend about 50 bucks on cards and I wanted to know if it's still necessary to buy a Core Set to start with or can I buy other stuff instead. I'm just playing casually at home and don't intend to play in tournaments. Thanks

I wouldn't say its necessary to buy two copies, but you do need at least one copy.

In addition to the normal cards, the core set also comes with a set of affiliation cards (each deck needs one and they don't come in any other product - plus, if you're learning the game they have a reminder of the turn order printed on them) as well as a bunch of tokens and a Death Star dial. The core set also comes with several of the series "main" characters you'd probably be happy to have, including copies of Luke, Yoda, Obi-Wan, Han, Leia, Ackbar, Home One, Vader, Emperor, Tarkin, Motti, Devastator, and Boba Fett. You could proxy the tokens and dial easily enough and probably even find a set of affiliation cards on eBay for not too expensive, but you'd still be missing out on a bunch of cool cards.

So my recommendation at least is to definitely get at least 1 core set. I'd actually recommend starting at 1 copy of the core set and 1 copy of Edge of Darkness as a good starting point for fun/casual play.

Core set gets you the tokens, the dial, affiliation cards and some of the best objective sets in the game. Absolutely get at least one.