I only "spend" gold on duels and arena, where I don't really lose any gold atm. The next expansion is only in 2 weeks, so you'll probably appreciate keeping most of what you have now. If you don't have that many MDMF cards, you have reason to spend a bit more now.
Got 6000 gold + saved now, not much dust, but I recently just went on a rogue collection splurge and crafted a bunch of cards I didn’t have just to have them lol. Have almost every rogue card now except for a few of the nearly unplayable legendaries.