I got my motorcycle endorsement about 5 years ago now and have been an avid rider every since. Here is my advice:
The MSF course is a MUST. The habits they will teach you might save your life. It is also very important to ride ATGATT (All the gear, all the time). This means never go out without protective helmet, gloves, jacket, boots and leggings. The gear may not only save your life, it may save your largest organ, your skin. Also, remember it isn't a matter of IF you will take a fall, but rather WHEN.
Ride you own ride. Don't let anybody push you into riding farther or faster than you are ready. If you need to stick with parking lots and roads with little traffic for a while, so be it. It will take you about 2 years before you really feel at home on a bike. When you are ready to buy a bike, it is also better to start on what you are comfortable with, rather than buy the one you hope to grow into. It is just like horses where a new rider on an advanced horse is more likely to lose confidence and give up, or get hurt.
Ride like you are invisible and everyone else is out to kill you. DEFENSIVE driving is most important on a bike. Other drivers don't mean to cut you off, etc., but they can't see you. Bright colored riding gear will improve your visibility.
Lastly, enjoy the sport. You will meet some great people and experience scenery and travel like never before. By taking appropriate precautions (ATGATT, MSF, etc), you can lower the risk and make riding much more enjoyable. Good luck and have fun!