Thank god I don`t have to do this anymore! took me AGES to get. I got lucky when the machine was "on fire" started playing it manually (i`d probably recommend that you do that to get the 130% bonus which is reduced to about 99% on auto-play) got lucky enough to get into victory mode and then super victory mode. This is where I got really lucky, on SV mode i managed to line up 3 9s which gave me 5000 coins (playing at 100 coins of course) a while later i mananged to get another row of 9s and thus aother 5000 coins. I finally got the lucky coin.
As far as how long it takes to get 7777 coins that can vary. Unless u get lucky, like I did, the machine`s payout is extremely low, forget hours it could take days or more to get it (especially on auto play). I can`t give you an accurate time because like I say it depends on how lucky you are and also how long you are willing to play for if your not using auto play. Seriously, I hate those stupid slot machines so much. You lose more than make a profit.