Rule #1: Be reluctant with purchases - there's new and better offers at every level, and they come daily in the beginning.
Rule #2: Be aware that tiering up will put you further back in tees and course length - big buy necessary at Master tier, then again as a Legend.
I'd start with one (64°) or two (64, 60°) short wedges but not before L28. Then a 3WD as a budget replacement for the Starter driver, irons according to your money bag's size.
Putter, not below 500 cr. This helps you to do your practice chores before deciding.
Custom balls are worn and lost - a constant draught of credits. Start cheap - B-ES or Tour-SD - to get experience with this fact. My rule of thumb: No balls better (in level) than your main clubs.
The Stand Bag doesn't influence the game - the description is exhaustive. Different to that, me thinks it's ugly and a waste of 400 cr.
Stand Bag Plus holds four sets of clubs&balls, easing systematic changes before a game. Read the post on top of Bug Log Forum before selling unused clubs. More designs but still ugly IMHO.