@blessed1ofhis My thoughts on gear : Honestly I would recommend to almost anyone to buy the adjustable bells unless they aer one of those people who are like "I'm always just going to use a single weight bell and don't care to do more."
For someone who expects and intends to move up in weight (especially for guys, who tend to be buying heavier and thus more expensive bells), by the time you've bought 3-4 retail bells, you could have gotten one of the adjustable bells instead and saved a lot of floor space and gotten way more adjustability.
As for number of bells...to me that depends on what program(s) you choose.
I just finished and am doing another of Geoff Neupert's programs, both of which expect and work best with dual bells. So, between dual-bell programs and also just having the feeling that I may occasionally want one bell at one weight and another bell at a different weight *within the same workout*, I bought two BoS adjustables and couldn't be happier with them. Great product, and honestly ~$500USD isn't so bad for two highly adjustable, high quality kettlebells.