I know you need gems and such (I read the FAQ) but how exactly? I went to the caves to dig up gems, but nothing. Are they only open on the 6/7th? How hard is it to dig up gems, how many do you need, etc?

They are only open on the 6th and 7th of every month. There's no difficulty to digging up the gems, there is just a wait in between times when you can dig, between 1-3 hours. I can't recall how many gems Itallo asks for, I think it's about 4 or 5.