Originally Posted by
Kralljin
If you start out on Neutral / friendly, you have a hell of a ride before you.
I don't know how much a WSG game brings rep wise currently, last time (Which was on Wotlk) is around ~35 per flag.
According to wowhead, you need 1200 turned in Flag in total.
That is 400 WON games in Warsong Gulch, taking a 50 / 50 Win / Loss ratio and add some 1 / 3 ; 2 / 3 Loss into account, you'll need around 600 WSG games for the WSG part alone.
Granted, it is the hardest part of the Achievement but i highly recommend doing it on a character on which you really enjoy PvP or have already a serious Rep advantage.
I remember doing it in Wotlk and it was a pain in the ass, even on a character which started out on halfway to Revered in WSG and Arathi basin.
edit: you gain now 100 Rep per Flag.
so you need 420 turned in Flags => 140 Wins, still a fucking lot.