mine either go in a cardboard box or on the floor in a heap by the modular (note my modular is also on the floor not a desk - due to position of TV - for video synthesis)
as for the optimum number of cables - to start with count the number of sockets in your modules and divide by 2... get a selection of lengths - up to a bit bigger than you think you need so there's some slack when patching
as you get more modules the ratio of cables to sockets will reduce - you probably won't patch every socket of every module every time you patch
I tend to buy cables in batches - 15 to 20 at a time - when I notice I am getting low at the end of a big patch (especially if I am planning on getting more modules soon) and possibly a couple of stackcables when I buy a module - especially if i need to add a few € to get free shipping
currently I'm really liking PolarNoise for 90-150cm braided cables and befaco for some very long cables (3m) - I also like the Black Market Modular cables
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities