^^
If you can, I totally recommend the pre-sale the day before the concerts start! I arrived at the dome on Friday at about 11:45am. This was everyone that was there:
I'd say less than 100 people. At around 12:30pm, this was everyone behind me:
Seems long, but I can still see the end of the line at the time so it wasn't that bad. It probably definitely helped that it was Friday so most people still have to go to work and school and everything.
Goods started selling at 1pm and I finished by 1:20pm. Quick, no hassle, nothing sold out, and no buying limits (at the time). Like there was a guy in the line next to mine and he bought 15 PHOTOBOOKS (among other things) lmaoo.
The keychains seem to sell out the quickest, so if that's what you want then I recommend going as early as you possibly can if you're going on the concert days! Otherwise, you should probably be fine in getting everything that you want on the presale day. I had no problem buying both the black and white keychains.