I love Vegas and go for the shows and to people watch. All the suggestions on the previous posts are excellent ideas. I would highly recommend watching the fountains at the Bellagio at night/seeing the beautiful flower garden inside, Fremont street at night (check the light show schedule), and walking the strip in comfortable shoes. It can get chilly at night in October, so bring a jacket.
Here are some useful websites to save money:
Tix 4 Tonight
Events in Las Vegas | Goldstar
There are a lot of great photo opportunities, so bring a good camera and enjoy your time.