it might also go without saying, but I think part of the reason there is always so much module buying/selling (besides people liking to buy stuff) is that there are all sorts aspects of modules that make one person get along with them and another person hate them. The person who really likes Maths probably wouldn’t care for Quadra, and vice versa (I think I’d be in the Maths camp there for the logic, mixing, and more CV control, but I like generative/morphing stuff). I say just get whatever you instinctively are drawn to and go from there. If you buy used, you probably will only lose out on a few dollars for shipping, and if you buy new, you’re likely only out 20% if you decide to sell something.
Also, Peaks is an EG, as well, so you could totally get by without Quadra or Maths at all to start and you’d still have more EGs between Pam’s, O&C, and Peaks than many other racks of comparable size.