[Fat Charlie]

Step back and examine what you're asking:
...gas bill has been adding quick and I have started to look for good looking efficient car that I can modify.
But I do not care if I get my money back after modifications from saving gas so please no preaching about how I drive.

Your ideal is ... modify it to get +100mpg?
But ...it can not look like a Prius.

As an aside, do you know why a Prius looks that way? It's because math doesn't care about your feelings.

Anyway, you say you don't like the money you're wasting on gas, but you "can not" be seen in something that doesn't burn much gas. You want to be seen in something cool and bang a wrench on it to make it give you magically high mileage, but don't want to operate it in a way that increases its numbers. Because racecar (and keep it quiet, but also wallet).

You get efficient results by taking an efficient machine and operating it efficiently. You can take an inefficient machine and modify it to be more efficient, and that's great. If your goal is "look what I made," then go for it and enjoy the hell out of it. The biggest, most effective mod, though, is adjusting the nut behind the wheel.