I highly recommend using manual settings as much as you can. Its digital, you can trial/error as much as possible. If you just use it on auto...kinda no sense in it really as then you are just using it as a point and shoot. Play with what you can do with all the manual control. Dont know how much you know so sorry if this is patrionizing. There are 3 main factors and all in some sense control the amount of light in an image. But all have their own give and take.
ISO: lower values give less light, but less grain. Higher values make images brighter, but you get to have grain issues.
F/stop (aperature): how wide open the blades are. Lower number, more light is is let in. But you loose depth of field for focusing the lower you go.
Shutter speed: how long the shutter is open. Longer its open, more light can come in and brighter the image but eventually you'll need a tripod/something to set it on and a remote to trigger it so you dont get any camera shake blurring the image. FWIW if you practice, it is possible to hold steady, I can do a hand held image down to 1.5-2sec with no blurring.
As for lenses, do not be afraid to stalk ebay for deals. If Cannon is anything like Nikons, the same mount has been used for ages. If you are comfy with your manual settings, even if it doesn't have the fancy computerizations of the new lenses you can use them on manual (any other settings and the camera wont detect the lens and wont shoot, least that is how it works with nikons). Old glass is oftentimes very good. Ive picked up a zoom macro lens for $20. Something if I had gotten the newest version of, it would be easily up to $1000. You just want to make sure there is no mold, moisure, or scratch damage on the lens. Most sellers who know what they are talking about state specifics on these things. Those are the ones to trust more than the person who is "oh I found these old lenses in my closet sold as is" - you have more risk there.
As for the crop: Wiki actually explains this well (I am a visual person so me likey) http://en.wikipedia.org/wiki/Image_sensor_format
Oh and eta: to the skateboard person - remotes are AMAZING and like $10. Cool photo but just you know, to make things easier next time! =)