Leaving the camera in auto can also cause these problems. If you don't spend some time playing with the camera and learning what it can and can not do, it won't matter if you buy a $50 or a $5000 model you won't be happy with the outcome.
Something as simple as placing a cheap point and shoot camera on a tripod and then selecting the night portrait feature will greatly improve your low light hero shot by better exposing the background and then providing a pop of flash just before the shutter closes to freeze the subject in the frame.
The ability to change how the camera meters the scene can also be important when taking outdoor photos. You see this when shooting with a bright background and a back lit subject. You can either use the normal metering and fill flash in hopes of lighting your subject properly or use spot metering and expose the frame for your subject which will cause your background to be overly bright but if you aren't looking for much detail for the background this is fine. Or you can combine flash with spot metering to hopefully achieve the exposure you want.
If grainy or noisy is the issue then the camera is selecting too high of an iso because it thinks that's what you want. I often pre select the iso I want the camera to use or limit the max range the camera can select when it is allowed to select iso.
There are three basic functions that need to be controlled, iso, aperture, and shutter speed. Learning to take control of one or two of these at a time will greatly improve your photos with even the cheapest camera. Throw in metering and you have a lot of what it takes to make an image.
There are a few quick and dirty outdoor shooting guides out there that I can think of, Nat Geo has a good one. There is an easy to read series of books from Scott Kelby that are very useful as well, though not outdoor specific. PM me for more specifics on the books.
