Modifications on a Budget: What to do now?

Are there any suggestions or requests for certain modifications for your car? I am still working on mine. There are some small things wrong with it, there is a small fuel leak and an oil leak I need to take care of. I have found the parts for it and just need to work on it and fix it. 

I plan on getting a wide band O2 sensor, it measures the air to fuel ratio. That will probably be it for a while, it is taking a lot more money and time than I thought to get the car fixed. 

What modifications have you done to your car? What modifications do you want to do to your vehicle? Leave a comment below.