New to Photography

I want to get into photography and don't really know a whole lot about it. I enjoy taking pictures and playing with them on my mac, but i want to take it to the next level. I want to start taking some good shots of our riding.I want to get a decent camera but can't spend alot of money. I was looking at starting with the canon Rebel xsi 12.2 or 10.1 mo digital slr. Any opinions would be helpful. thanks
Heres a few I took with a canon powershot 7.1mp.