After about 3 days of digging now I'm at Level 1, and nearing 2...I say this because I've started to dig up petrified logs...something I didn't before...yet another sign that *gasp* chocobo digging skill is in fact...REAL!!
Enough sarcasm...I've mashed everything I know about this so far into one very easy to read HTML doc, that I plan to update...its also got a few tips for beginners, ect...hope everyone enjoys. When I start into other areas I'll post up what I dig there and which days are the good ones...as far as good and bad days to dig...its not BS, its tried and tested...the difference between digging yhutunga on fire day and ice day, is barely breaking even, and making 20k profit.
Ultimate Chocobo Digging Guide
Also please note the prices in the guide reflect the prices on Ifrit, they will probably vary on your server.