This is the simple answer. Other people here can give you better information. Luckily, they got rid of rookies in open league so don't worry about them. Draft at least 19,300 minutes, but if you draft too many minutes it's money wasted. Defense, rebounding and eFG% are all important. You should have at least 100% combined usage on the court at all times. Learn about usage tiers. Assists are good, turnovers are bad. (Like I said, this is the simple version.) Players will usually not get to the free throw line as much as they did in real life. Try to have a good balance between inside shooting and perimeter shooting. Join an open league and give it a shot. Look and see how the best teams were built. Don't copy anyone straight up, but you can get an idea of what works and what doesn't.
Most of all just have fun with it. It's a game. Good luck!