Don't buy a Garry carry (at least not for the heirloom). They are boosting the heirloom drops to a guaranteed drop for each toon... and the flex is just as good while leveling as the norm one.
Like others have said, stacking up some gold is a great idea.. With the ability (as I understand) to get items from other professions from your helpers in garrison and the decrease of profession bonuses I'd be willing to bet that the item enhancements are gonna run a pretty penny.
If you have alts, now is the time to finish getting them level capped and grabbing some welfare isle gear... it'll make it much easier to level them once the expac launches. Also, it'll let you evaluate some other classes if your main gets hit too hard.
Gold wise, it's hard to say. I'd go with somewhere between 25-35k just for the garrison, initial enhancements, etc..