What you want to do is choose 1 color to be your main focus. Buy pretty much only that 1 color. The only exception to this is the following choose another color that can can built on the main focus color as your secondary for example if your main is white, you can choose either blue or red as your secondary but not gray. Buy your secondary color only if you are behind in rooms compared quota. Id say to be comfortable get around 1.25-1.5 times as many cards as there are for this quota. eventually this will no longer be an issue as you get lucky enough with your main color with how many opetunites you get. The way i got this score was buy buying a good ammount of the 30-40 floors (i like to call them double down floors) and risking my ruin with them a few times to keep the streak going. Do note i only really started doing this with double down floors when my chance of main color was above 50 percent. Some luck is needed but once you get going you get going.