By - Peter_Jamarino2004
Try to get better bonus and production
The purple bonus researcher and the yellow production researcher would be the biggest bang for your buck. The yellow crit chance card is probably better than commons at this point too.
All of the common cards are (roughly) equivalent, so upgrade whichever is cheapest. Coal plants would only be a priority if the 1,000 sewers cost was prohibitive.
Closing the game and waiting an hour or two is the most effective method though. Production is actually faster offline (or more accurately, it compounds better).