I have almost a complete collection, missing mostly trash legendaries or epics from each set. I would like to have a complete collection however, and I have quite a bit of dust saved, so I'm wondering what's the most efficient way to go about it. Any tips?

Buy 120 of any pack, see if you get the missing epics/legendaries

If not, atleast you get like 7k dust out of it to craft x)

buy packs/do arena until you have enough dust to craft the rest of your collection at the same time

arena

use an excel sheet. do not ever craft a card of a set, ever, unless you can craft the whole set at once. Never take those packs again.

so my guess is that GVG might be the first one to craft because we get lots of classic packs from quest/tavern brawl.

makes sense, i did classic first because brawl did not exist back then.

dont do that if you play arena