Sfs, couple of things. And if this is all pretty basic to you, my apologies in advance.
I pulled the pic to my desktop and viewed the exif data. It was shot at ISO200, 1/160 sec @ f5.6 and 55mm. I'm a Canon shooter, and most generally shoot in aperture priority mode (Av). So in Av, when you spin the top dial, you are adjusting your aperture, and the shutter speed self adjusts to go along with it. Manual mode is great for certain things, but today's DSLRs have excellent metering systems, and the 400D is very good camera. I'd set the metering mode to evaluative.
If I can offer one other bit of perspective, it's useful to get in the habit of checking the histogram on the LCD after taking a photograph so you can fine tune your settings. Also, go into your menu and enable the highlight warning. This allows you to see on the LCD any portions of the image that might have blown out highlights (overexposed so there's no data in them). Those areas will blink, which is why they are called "blinkies," and you can use exposure compensation to underexpose in 1/3 stop increments until those areas stop blinking.
I'm assuming you have your owner's manual if you aren't sure how to make those adjustments. As you progress, you'll see what a blessing it is to have rapidly adjustable ISO. Shutter speed, aperture and ISO are the interlocking trio that make it all go round.
The four predominant washes of color in the image are quite nice. The white trunks and orange foliage to the left, and the green foliage and lavender blooms to the right balance each other nicely. You've also composed it in a pleasing way. If you wait for muted light, either full shade or a cloudy day, you'll avoid the contrasty "hot" look you get from strong shadows produced by the sun.
The best bang for your buck with that camera and a zoom in that focal length range is the Tamron 17-50mm f2.8. It is really sharp through the whole zoom range, and is specifically designed for the size sensor in your 400D. When I was using the 20D, 30D and 40D, it was my go-to wide angle zoom. It's also nice to have that extra stop or two of speed with an f2.8 lens. It can be had used for around $300 USD. Check out the Photography on the Net classified section. I've bought and sold thousands in camera gear on that forum with not a single bad experience. They have a huge worldwide membership.
Aside from having to "zoom with your feet" when using the nifty fifty (also called the plastic fantastic, BTW), it's a great cheap lens. Sharp as a tack! And if you don't bang it up and don't mind a slower autofocus when using it, you'll like the results. I keep one in my kit in case of emergencies.
Photography is a big ton of fun, and I wish you the best of luck with it.
/www.carmarthencameras.co.uk/
