Doing small mods (ie reversible stuff) like wheels etc is fine mate, nothing wrong with a few choice mods, but never do anything you can't take off - example being if you fitted a set of 15 inch alloys with decent tyres, then fitted a set of quality lowering springs, this would cost you around £500 and make a nice difference to the car - then when you have saved up enough, swap back to the original springs and wheels, sell the aftermarket ones and sell the car as standard.
If we are taking a short amount of time then save and buy a renaultsport