My $.02
riding class/course (as others have suggested); not sure where you're located, but there are 2 Harley dealers local here in KC that I know of that have their own designated area/practice/course where they offer classes. My brother signed up for a class at a local Community College when he started out.
Find a small, cheap bike to learn on/ride/improve. Vstar 650 would be fine (I rode one for probably 3 years). If you re interested in that Cruise segment, any middlweight 650/750 UJM will be fine. Something cheap enough you won't be upset when you dump it at a gas station, parking lot, driveway; or some other slow speed oopsie. you will do it....everyone I know has
myself included.
Then start logging miles; and keep practicing. hell, I still go out fairly often and just practice a particular thing; slow speed manuever; emergency stop; trail braking; etc.
Don't ride above your head; becoming very proficient with motorcycles takes time. Take things slow.
Buy gear / set aside a good chunk of cash on good gear. This is a divisive sugject as you'll hear from both sides. I'm a gear guy. i've been down twice; once in full gear on my Ninja 600; only suffered a broken bone in my hand. Went down in t=shirt , jeans, boots and helmet on my Street Glide about 5 years ago; beanie helmet was caved in (would've killed me if I didn't have it), and I slid on my back, shoulders, and rolled to my foreamrs and slid on the pavement around 45mph. Road rash sucks . Just wear gear. I think there are even some rash pics in this thread somewhere.
If you're debating on whether to get gear....next time you're driving 6o MPH down the road in your car, ask yourself if you'd open the door and jump out of the car. If the answer is no....buy gear.
quite a few good youtube vids out there as well.
one comes to mind is Motojitsu series. would be a great resource for beginners and experienced alike.
Twist of the Wrist is another. it's older, but it's great info.