Find a car that doesn't need any major work. And don't change the interior color. It costs a lot more than you think to do repairs and they're not always successful afterwards. Then what do you do? A convertible is also not a great car for a first car. They didn't sell that many so not too many people have them here so can't really give you any advice on it. If you have any issues with the up/down mechanism, you're going to hear crickets for help.
And what's the mileage of the car? If the seats are worn out, that's not a good sign. If the mileage is high probably lots of other parts that are worn out and will need replacing. You basically need several thousands handy to keep up with normal repairs as a car ages. Brakes, transmission fluid, springs, struts, shocks, upper/lower control arms, ball joints, tensioners/pulleys, motor mounts, sway bar links, tie rods, etc. Even a used engine is anywhere from $2500-$4000 with a very short warranty. And that doesn't even include labor.