Im a P plater aswell. I havent made the smartest descisions when it comes to cars but i can give you some advice.
1. I would steer clear of body kits, purely for the fact of we are in-experienced drivers, and 'kit' driving can take quite some getting used to. Fiberglass is very delicate compared to the stock plastic bumpers and can crack at the smallest of impacts. I had a full kit on my nissan exa, and after i got rid of it i swore i would not buy another kit until i was a crapload better at driving.
2. Find a car which is what i call 'granny spec'. Untouched, unmolested and not modded. Stock as a rock in other words. I have seen some dodgey backyard jobs and its not worth it. They may be harder to find but i swear to god its worth it.
3. This isnt really advice for finding a car, but more for when you get your car. When modding your car (im guessing that you will) keep the mods clean. Dont go and mount fully sick neons everywhere. Keep stuff tidy, maintain your car well. And if you feel that a job is over your head, dont do it anyway. Chances are you eff something else up which will lead to more $$$
4. Also keeping your car legal is also important. P plater + import = harrasment. I drive a R32 GTS and get pulled over now and then, and there is nothing better than knowing that the poilce cant defect you for anything.
Hope this helps, Mitch