What to stock up on?

This. I bought ~100 diamonds for under a dollar in the MTS a while back, and while I'm not gonna make as much as some of you guys, if they're even close to 1m each... that's an amazing amount of money for me.

I've gotten 100 power crystal ores for 221 nx (22.2 cents) twice, and several times gotten 100 for 1200 or less through several deals. While it may seem pricey, figure that that is 5-6m for 10 crystals, which, if they sell 1m each minimum, is profit.