I was very conservative on my first kegging venture, but instantly "got it." This may be because I had beginner's luck and everything has gone very smoothly, but I am feeling very post-bottle these days.
Because I was conservative, I bought one (3-gallon) keg, a 5-lb CO2 canister, and a Taprite single-body regulator (plus pre-assembled gas and beer lines). I brew small batches so the keg size is perrrrrfect. Sold on kegging, I have already bought another 3-gallon keg from AIH during their Presidents' Day sale and am contemplating taking advantage of the Williams keg sale this weekend on kegs to get one more.
So about regulators. My expectation for the next year or so is I'll have up to two 3-gallon kegs on CO2 at any one time, though with the fridge I have for my kegs (a hand-me-down from my landlord), I could fit three or possibly more. I expect to get busy next weekend and every weekend through the remainder of 2016 with my grad studies, so I am assuming I will brew more than 2015 (three batches) but less than 2014 (not sure, 6-10?). Life could change that, but it's a plan for now, anyway.
I brew different styles; right now I have an oatmeal stout on tap as my first kegged beer, and today brewed a rye IPA (*waves at Denny*), plus have a Belgian tripel in bottles. Should I try using a splitter? Get a dual-body regulator? Get another regulator and canister? What do people do?