Here’s how to grind:
leves, bone harpoon butts, copper nuggets, brass nuggets
copper earrings, t1 gems, and silver nuggets when you can (would be wise to start stocking them)
up to r25ish:
brass earrings then phase into brass rings (require the same mats, get a feel for it)
brass rings mostly and electrum nuggets when you can (would be wise to start stocking them)
silver ring into silver needle when you can reliably do it
silver needle will go as far as 41, though slow, it is super cheap to grind. can also add in some silver chakram, tier1 gem rings, and white coral (arrowheads i believe)
electrum rings (time to suck it up. mats are gonna be pricey, unless you can mine gold. And if you were thinking about leveling miner, and arent in any real hurry… now would be a good time.)
silver francisca, mixed in occasional t2 gem rings, could keep going with electrum rings too if you’re a masochist.
also red coral. but in my personal experience i find coral to be hilariously rare and mediocre, not something anyone should expect to grind off of. I personally never really reliably grinded coral, just like 3 or 4 synths per rank. Maybe someone can post an efficient way of collecting coral.
Note: Silver Francisca mats will require CRP20ish (ash francisca haft) and ALCH40ish (scale glue). Should not be too much a prob though. Especially if you’re coming down off an expensive electrum grind.
Hope this helps. I’ll tell you now the electrum grind is brutal, and may turn people away from GLD for the time being. It’s only because the gold sand/ore market is so expensive and controlled by miners (their prices are justified). Depending on your bank you may wish to put your GLD on pause at this stage, it may be safe to assume that something in the future will happen that will cause gold to decrease in price. (and really, this disclaimer is mainly for those who are interested in leveling gold from the beginning. They may find value in knowing of this situation way beforehand. For the rest of you who are already 40+ and climbing, carry on! Godspeed!)
If you find yourself doing a bunch of faction NM leves, keep an eye out for Drake Collar drops off the Branded Drake type mobs. Ask your party members for those. They synth into 8 electrum nuggets and chances are those people are just going to vendor them for nothing.
Guide compiled from personal experience and a few references on other forums.