What to stock up on?

Personally, I'm expecting stimulators to become several million mesos each. Since you can only use one Diamond, Black Crystal, and Dark Crystal on a weapon, it's the only other thing that gives you variable attack on your weapon. Not to mention the shoe and (i believe they exist) overall stimulators.

Stims drop fairly often compared to certain equips and scrolls. That's just my experience anyways.

What does shoe and overall stimulator raise?

Defense and other stats? o.O Just like a regular weapon stim.