Is my bike worth fixing or should I just buy a new one?

Today I found my old bike from back when I was a kid. I'm 20 so this wasn't so long ago. I decided to fix it up but I've ran into a few problems. I don't know anythinga bout bikes so I'm not sure if this is worth fixing or if I should just buy a new one. First off, the chain is a rusty mess. Second, the inner tube on the back tire is deflated and all tangled up in the spokes and chain. The seat is covered in mold and most of the caps on the handle bar are gone. It was never some high quality bike, just something I got for my 11th birthday at Toy's R Us probably. I'd really appreciate it if someone out there who knows alot about fixing up bikes could give me their two cents. Thank you.