Welcome to POTN...
Once you get your feet wet with a body and a basic lens and have begun to get a feel for where and what you like to shoot, then you can start to think about future equipment purchases.
If you find yourself doing a lot of shooting indoors or in very low light, a flash can be very handy. Honestly, filters aren't really necessary at this stage in your photographic development. A spare battery isn't a bad idea if you tend to find yourself out all day looking for good scenery or interesting people and won't have the chance to do any recharging.
A rigid lens hood would be a very wise thing to get. Hoods have saved the day on several occasions for me and they're much cheaper to replace than an entire lens or even just a front element.
I'd suggest you also look for the book "Understanding Exposure" by Bryan Peterson. It does a good job laying out the basics of the relationship among shutter, aperture and ISO.
Be sure to spend some time reading "Stickies" in each section of POTN (Gold Mine of info) and don't be afraid to offer your opinions of other's work if they ask for C&C (Critique & Critisicm) Just be sure to respond in kind and post some of your work as you go.
Good Luck!! 
