What sport bike should I get?

I've saved up some money for a bit. But the time has come where my parents won't let me use their vehicles anymore and I don't have money to pay for a car so I'm left with getting a motorcycle. I've rode a stupid small *** crf70, and goofed off with my friends ktm500. I will need to ride 10 miles on the freeway going 75-80 for 5 days a week. So I don't think I should get a cbr300r. Or ninja 300. I'm looking at the honda cbr650f, cbr500r, ninja 650, suzuki gsx -r600 (I think would be too much). I'm not an idiot, but I also don't want to overwhelm myself. I need something with decent Gas milage, cheap, but can also hold its ground at a constant 80 mph.

The 500's and the 650's are great starting platforms that offer cheap insurance, reliability, and economical ownership costs (gas, tires, maintenance, etc…). One of the best purpose built commuter bikes is the new honda nc700. It is one of the easiest to ride bikes I have ever ridden.

If this is your only means of transportation, get a car. Being required to commute on a non weather insulated vehicle gets old fast outside of riding season, trust me, i commuted to work and college for over a year with just a motorcycle.

If you are dead set on a bike, any of the bikes you mentioned (except the gsxr) are good choices. Even the 300's will go over 100mph without breaking a sweat, so they are plenty capable on the highway. A 500 or 650 will be much more comfortable though.

Depends on how big you are.

Since I'm slightly bigger (6'0 205lbs) when I had my 250R and 650R bikes, they got roughly the same gas mileage. The reason was because the 250R was light enough, when traveling at freeway speeds, I provided a lot of wind resistance. In town driving however, the 250R will win in MPG every time. Probably average around 45-50mpg on the 250R, whereas the 650 will average around 40-45.

So if you plan on being on the freeway a lot, I would lean more towards the 650 because it weighs more and won't get pushed around in the wind as badly. While the 250R is plenty fast enough to be on the freeway, (I redlined it at 95mph) your arms get tired fast from correcting wind shears. Also since to maintain freeway speeds on the 250R, you are usually hovering around 9-10k RPM (red lines at 13k), so the vibration gets to you after a while too.

So in summary:

250R gets better gas mileage in town and occasional freeway travel.
650R will get the same gas mileage if you spend all of your time on the freeway, but less gas mileage if you do a lot more in town.

They cost about the same to maintain, while the 650 will have a little higher up front cost, and a little higher insurance. (However since it is still a vtwin, the classified as a standard and not super sport, insurance isn't bad.)

If you *actually* want "something with decent Gas milage, cheap" you will get a 250 -- a Ninja 250, CBR250, TU250, or GW250. All will be just fine doing 80 mph for 100 miles.

What you will get will be a 650 far more cost to start and pitiful gas mileage.