just go and shoot your gun. dont worry about guns/minor/major..
first learn, when you overcome your gun, then upgrade your equipment..
the xdm9 is a very nice gun and you can do pretty well in idpa/uspsa with it.
and when you decide to shoot limited, get a 40. 45 is not a good idea for limited, unless you want to shoot limited 10. it does not worth get gun for limited and be in disadvantage with the very good shooters. if you are a beginner and own 9mm pistol, production/ SSP is your place to start with.
focus on the basis, trigger control, grip, transitions, align the sight while shooting fast...
dont do as many guys who get expensive guns and are not that good.. it is not the arrow, it is the indian.