sweatdrop Sadly most of the "active" Tuna crewing threads have closed over the past few years, but you can try asking Rainbow.
Just a note - Tunas usually take a few days to schedule (getting crew members, getting powerups, etc.), so you probably won't get one "ASAP"
Make sure you're around 11.4 CL with this ringset: 4 attacks, 2 buffs, Fitness (or a different passive), and Meat (or another passive/attack)
You're going to need at least one pack of Revives and probably one pack of Ghi Amps.
Plus the runs can last anywhere from 2~6 hours, so make sure you have plenty of time to spare 3nodding