Hi Aaron and welcome to the forums.
Friend requests that you send out must be accepted before you actually can be friends. Some folks prefer to use their friends list as a way to keep in contact with people they know or have played with before. Since you're a relatively new unknown player it may take a little while to build up some "cred", but you'll be loaded down with friends before you know it.
There are a couple of ways to earn credits right now. This
blog post covers all of the various options. Give it a read through and you'll be on your way. One thing that is not mentioned in that blog are the promotion bonuses you receive for advancing through the tiers. You'll receive 50c for reaching Amateur, 100cr for reaching Pro and 200cr for reaching Master. Progress at your own pace though because some of those Master tier players are exceptionally good at this game and you don't want to be in a tier that is beyond your ability. If you play and post all of your scores (good and bad) then you'll be nestled right into the tier that you belong in with players of similar skill.
The best way to get practice is to just play. Ranked rounds will affect your scoring average and you will earn promotions as your skill level increases and your average decreases. You can also choose to do Practice Rounds and those do not count towards your stats or average.
Some courses are only available as a CTTH (Closest to the Hole) challenge. At this point in the game there is nothing that you need to unlock. You can play full tee to green play on Bethpage, Kiawah Island, St. Andrews and very soon we will be adding a 4th full course, Oakmont Country Club.
Good Luck =)