I've been riding since I was 14, almost 21,000 miles accumulated so far and im only 21. never had a ticket in my life.
Get a 250 first (if your thinking sport bikes). You will be soo much more experienced and less likely to kill yourself if you experience a 250 before the bigger bikes. Most professional riders interviewed have admitted they started on a 250cc. The new honda cbr250 looks promising, but the most common starter sport bike is the Kawasaki 250. Which is an awesome and very reliable bike. I personally chose the niche bike, Hyosung GT250R which needed very minimal maintenance. I have stopped at the CBR600rr and wont go any higher unless its an sv1000 or similar for long distance road trips.
High miles is different from bike to bike.
Typically an sv1000, sv650, any touring BMW, Honda, Kawasaki, Suzuki,Ducati will been seen with higher miles up to 50k 60k area. Sport bikes are typically seen with less miles, 20k and below. high miles for a sport bike i would say is over 20k. A lot of guys in utah rebuild the engine around 20-25k miles.
I personally stay away from Harley/Buell due to the bad quality and break-downs I hear from guys that have been riding for many years.
With gear, obviously the more you pay the better quality (mostly).
I suggest to research each item you buy.
Motorcycle Superstore - Motorcycle Accessories and Motorcycle Gearis my favorite only site. They have video reviews on a lot of the protective gear being offered. The shipping is fast and cheap. And the customer service is top quality as well.
I suggest to purchase a jacket that suits your riding style (mesh-summer vs textile or leather), you should buy higher quality gloves because when you ride your hands will numb up if you have cheap-o's vs padded leather ones, your helmet should be up to date and not an old helmet. I suggest getting a new helmet with your preferred shield and take into consideration the air flow into and out of the helmet, but make sure you try on the sizes first at a local shop because each brand is a little bit different.
Never ride with sandals, always ride with shoes that cover most of your ankle and wont slip.
Please dont think your the shit on your new bike or you will die.