I haven’t used any gdkps or bough tokens as doing raids in cata gave you a lot of gold and if your guild is selling boes they should be able to give out cauldrons and feasts. I have slowly made more gold than I spent in cata with simply raid login for long. Doing dailies in Tol’barad and Molten front also can net you a lot of gold which makes it easy to pay for other consumables/enchants/gems. (I have farmed those a bit to make sure I could buy the great expedition yak which is a mount that cost 108k gold in mop)
The only things that cost a lot are boes which are pretty much for people that do gdkps same as darkmoon cards which can cost a lot. You could technically buy tokens for those but really they aren’t necessary to do content.
I don’t think there’s any new servers in mind as the last time they did in wotlk they failed and with server population being much smaller as back then it wouldn’t make much sense imo.
In Dragonsoul there was also the epic gems problem which made those incredibly pricy but Blizzard made those epic gems much easier which made those way more cheap.
Mop raids should also be worth a decent bit in term of gold and there’s a good amount of dailies if you fall behind a bit. Like in wotlk with transmute there’s also many professions daily cds which you can sell for a bit of money which adds up. The tiller’s farm will also help you for consumables without too much time investment.
Something to note as my last edit is that older expansions inflated gold gains a lot so they naturally make it easier to come back until around Legion/BFA.