Jisii, Sounds like you did excellent with this purchase! Dean is an excellent source of Jap knowledge too (he's sure helped me enough...).
As for ammo, a box of Norma 7.7 Jap (technically, the round is designated 7.7x58 mm) will get you started. The ammo is usually pretty steep price wise - upwards of $35 or more for a box of 20. If you plan on shooting it often, then dies are a good idea. You can get a set of Lee Pacesetter Dies from Midway or Cheaper Than Dirt for a reasonable price. If you do reload, here's a nickel's worth of advice: Arisakas have enormous throats, so don't be surprised to find your case necks expanded quite a bit after firing, requiring a lot of lube and force to resize. This is normal. I also use the Lee Factory Crimp Die (included with the Pacesetter set) to crimp my bullets... if I don't, I find the bullets to be loose in the necks - not loose enough to pull out by hand, but loose enough to spin the bullet in the case neck. If you buy Norma brass, make sure you anneal the case necks. The Privi brass comes already annealed. This will extend the life of your brass (because of the aforementioned neck issue). For my reloads, I load a Hornady 174 grain .303 bullet with 39.0 grains of IMR-4064 and a CCI-200 primer. This works well for me, and the 174 gr bullet is the normal Ball weight for Jap ammo.
Good luck, and let us know how she shoots!
Paul
"I was home... What happened? What the Hell Happened?" - MM1 Jacob Holman, USS San Pablo