With 5.1 nerfing the spawn rates of Ghost Iron by an additional 50% past the previous nerf, the gem market will almost assuredly start to tighten up with the lower supply of ore. Bots will come and go, but this nerf will almost assuredly drive out some excess player farmer competition.
Now is also the time to snag cheap materials (while they last) for upcoming patches that add new content.
Some things that should increase in value over time as the market adjusts to lesser spawn rates and fewer farmers:
- Ghost Iron Ore (obviously)
- Serpent's Eye - This is an iffy item to stockpile since we are past the days of i450 jewelry selling for high prices, however they are still worth keeping for crafting and sharding things.
- Uncommon Gems - Most can be had for as little as 1-2g per. Stockpile them for runs at perfect cuts or for eventual jewelery crafting.
- Rare Gems - Buy them in both Cut and Raw forms. Cut gems that are particularly useful but cheap are the ones you want to target.
- Golden Lotus - Snag any cheap GL you see for transmuting gems (I do orange since they still sell well). Typically a cut gem will sell for 30-40g more than the mats to transmute it. Throw in a few procs for extras on transmutes...
This is by no means a foolproof list, but a shrewd person who knows their market should be able to invest 10-20k and squeeze a 100% or better return on the investment over the next few months.