First bike: a dirt bike. Like a KLR or something you can make legal for the street.
Sport bikes are a niche market with a sharp focus on a small part of riding a motorcycle. For a first bike, I'd suggest a smaller standard or enduro bike. You need overall skills and road-sense more than you need the ability to drag a knee or wheelie. Sport bikes, I don't care what displacement are not ideal learner bikes. They possess radical steering, killer brakes, and a focused riding position. None of which is going to ease you into riding on the street.
This is a sport bike forum, a bunch of people will suggest a sport bike, just a little one. Remember your audience here. I suggest a standard or enduro for a first bike- no sport bike whatsoever.
Not that you can't possibly handle anything else. I'm not one of those knee-jerk, "you'll die in under 10 seconds on anything but an EX250" types. But I strongly suggest you become familiar with riding overall before worrying about the focus of a sport bike.