Heya mate
You're best spending some time learning some stuff in photoshop if you want to do it on a budget. I now have three flashes and a light booth for static shots - but I used to use a piece of white paper and photoshop for similar results (admitedly I had 16 lights in my kitchen!)
For the statics you can get a pure white background simply by changing the levels in photoshop - and as long as the image is fairly well photographed it will look pro.
Some cheap external flash would be a really good investment - mounted on the hotshoe of the camera and pointed toward your (hopefully) white ceiling it will give you a really good diffuse bounce-light. I always use full-manual mode when using flash / photographing static shots like that - they often come out slightly underexposed (dark) which is easy to sort out in photoshop (over exposed photos can't easily be fixed).
Not sure what camera for 300 would be good - tbh, I'd go for any DSLR you can afford for that money, even if it's 2nd hand. I use a 50mm F1.8 for a lot of static shots (and crop them for close ups sometimes) which are around 50-60 ukp for nikon / canon SLR cameras.
You can probably get a really good prosumer fixed lens camera for the money you're looking for that will produce some good images, but for the best images you're better off with the crappiest nastiest DSLR and learning how to use it properly.
