umm
i guess i'll give you an honest opinion
first pic:
sky is overexposed, if you used two shots (one to expose the sky, and one for the car, then blended them in photoshop, it would've worked out better)
2nd pic is good
3rd pic:
what dezz said, you have to turn the wheel the opposite way, noone wants to see your tyres
4th pic:
its tilted, but not tilted enough to be on purpose
also, photoshop out the car in the background
also, dont use such extreme angles, use whatever the horizon is, and also the lines of the car to match it up with other objects
you're not shooting for fast fours or some other ricer magazine, so no need for the gay angles
you say you want to buy a dslr, before you do that, learn how to use the camera properly, and how to expose/compose things correctly rather than wasting money on a camera that will just highlight the flaws in your photos