I have all of the books you do and this was my plan:
I started off with the MGMAT Quant books, One by one attempting the problem sets that accompany them. I did not touch the OG 12
/13 and gave it a pass for later. After i finished each MGMAT book
i did all the problems given in the relevant section of the Kaplan Premier
book (which i bought only for verbal and for the CAT's). After i finished all the quant books by MGMAT i started doing timed OG13 sets. I did sets of 30 PS problems at a time (all timed) and moved on to DS after finishing the PS set (and reviewing even the correct answers). In between my OG i used to mix up a few Kaplan 800
Problems just for variety, all the while going over relevant questions on this forum and from the materials posted by Bunnuel and others (GMAT PREP AND MGMAT SECTIONS, Tough problems etc).
This is where i stand now, Must have attempted around 2000 quant questions by now (in two months) from various sources (those GMAT specific that are mentioned, plus from online sources, high school books, and other test prep books (non gmat) ) . I needed to practice a loooooot because i had not taken a quant class in almost a decade, so if you are from a quant background then you need not practice as much as i am doing.
"When you want to succeed as bad as you want to breathe, then you’ll be successful.” - Eric Thomas