I think the first shot has the best focus. There was a plant like that when I was a kid, and it was called the "Dollar Plant" or somesuch thing...this is a cool-looking tree you have shown us, and you are right to go and shoot it right after rain--that's often an interesting time. The 2nd and 3rd shots have poor focus, but still, like frequency said, every picture has its lessons, its story...
RE: the Nikon D3100...yeah, it's a neat, low-cost d-slr, but right NOW, this season, I do believe you might be able to look around and find the D5100 priced even LOWER, due to the upcoming D5200 that will be available in Europe and Asia first, and available in North America ONLY AFTER Christmas!
Black Friday deals maybe?