You probably have too low an ISO speed with too small an aperture. If you're in darker areas, increase ISO and make sure you have a larger aperture (smaller f stop number) Provided you are shooting at approximately 1/60 or 1/125 secs.
Maybe you want to read an learn the very basics first before you use Manual mode? Your camera has automatic and half-automatic modes (Program Modes) fora good reason. Use them, you have paid for it, till to you know what to look out for to get properly exposed pictures in Manual. Photography Notes for Newbies
Maybe you can start with Av (Aperture) mode first and start learning from there. Then move on to Tv (shutter) mode and lastly manual. For manual mode, I usually monitor the exposure meter on my viewfinder to ensure that my shots are not under or overexpose.
There are no average settings. But if you keep the shutterspeed fast enough to handhold (faster than 1/60s) and shoot at apertures smaller than f5.6 (meaning f-numbers larger than 5.6, like f8, f11) your shots will turn out decently sharp if you focused on it properly.
Looks like you've underexpose. When you half press the shutter, look at your view finder below it is a scale from -2..-1..0..1..2. Try to make sure the scale is near the 0, then ok liao...hope it helps.