1 month of GPU is 12,000 points and I accumulated 17,000 points in September, although that included some bonus rewards for pre-ordering things eg. spending actual money on Starwars Squadrons, the Rocket League Season Pass etc.
With this being the 2nd of October, all I've done so far is completed the daily quests on the Bing searches and the two apps on the console, as well as a couple of weekly quests, to earn 821 points (ie. things that don't give me reward points for spending money). So taking that as an average I should earn 12,315 points over the course of this month by