from what I read in the rules
it says maximum 3 DS accounts per day (from the same warportal account)
and maximum 3 warpportal accounts per day
so from what I see, it's 3x3=9
I didn't test it (the time it takes to get that 100g is about the same as the gold I farm that's why I didn't bother to make that many characters),
so better have someone else confirm it
I already have 3 DS accounts from the same Warpportal account (those are made way before this event started)