Working for Disney is without doubt the cheapest way to visit Disney World and comes down to 2 things: Cast Member benefits and cheap rent. But you won't be entitled to any Cast Member benefits (food discounts, free park entry, etc) until after your first day of work a.k.a. Traditions. So here are some things you can do that won't leave you drastically out of pocket.
First up is Downtown Disney. Last year I was surprised by the number of people that didn't know that it is free to go there. There are loads of restaurants and shops to visit and you can spend ages just walking around the place, soaking up the atmosphere. I know lots of people are keen to go to TREX (or similar) early on in the trip and my one criticism of that is that eating in places like those can get very expensive really quickly. There is no doubt that the food is overpriced. Remember that once you get your CM ID you'll get discounts in a lot of those places so consider whether it's worth waiting to visit the more expensive ones after Traditions.
Another thing you can do for free is go and visit the hotels. There are plenty to choose from and during your first few days I recommend visiting the Polynesian and the hotels around the Magic Kingdom. Several reasons... firstly the beach at the Polynesian is a great place to watch the Magic Kingdom fireworks from so you can watch Wishes without spending a dime. Secondly, each hotel is beautifully themed and there's lots to explore. Thirdly, every hotel has a quick service location, many of which feature menu items that are also in their more expensive restaurants but for a fraction of the cost.
The next option isn't free but being a Disney CM won't save you any money on it so I'm throwing it in here anyway. Universal Orlando! If you're planning on visiting more than once then it's probably worth you getting an annual pass (which can also get you food and merch discounts).
Or what about more shopping? Firstly there's...ummm....Walmart which sells EVERYTHING but there's also The Florida Mall, The Millenia Mall, and the outlet malls. One of the outlet malls is right next door to the Commons and has a food court and stuff so provides another place to eat cheaply. (It's got a Subway, Starbucks, Panda Express, Sbarro etc).
Maybe you'd prefer to visit Celebration? It's a town that was built by Disney back in 1995 and it is beautiful and quaint. It's got some amazing restaurants, a cinema, and a great ice cream parlour too.
Speaking of the cinema don't forget that there's one in Downtown Disney and it's just about to start operating an in cinema restaurant as well. Basically you get fed a proper meal while you enjoy a movie - fantastic!
There's plenty of things to do in Orlando and at WDW but always try to make as much use of the discounts as possible. Loads of places will give you a discount (even non-Disney places) so ALWAYS ask before you buy.