The dragonborn fighter was the first one of those prepainted singles I picked up, and served as my dragonborn paladin in my at-work campaign until one of the other players painted me a mini. (I have never had anyone do that before. It was one of the nicest, and coolest, things anyone had done for me.)
Once upon a time, I had a ton of minis from WOTC-- Harbinger through Savage Encounters, plus Star Wars--but sold everything in a major scale-down purge. (It failed).
I tend toward WotC and WizKids products because 1. Prepainted, 2. Available. But after picking up the a full (brick? I forget the term) of Legends of Golarion, a drop box of We Be Goblins, and the Castle Ravenloft board game, my basic needs (or acceptable proxies) pretty much got met.
Otherwise, I'm pretty much motivated by "clearance." I'll still grab a booster if I find them on sale--my local Target had 50th Boosters on clearance a few months ago, and I cleaned them out at less than 50% MSRP. Took advantage of WizKids' clearance last year and picked up most of the Witchlight stuff because I was running the first chapter with my kids. Don't sleep on Barnes and Nobel, either--I got some of the flat mini sets for $7USD, and Pathfinder Skull and Shackles boosters for (IIRC), $5 USD (that find was a long time ago, though).
Online shops: almost exclusively MiniatureMarket, with occasional purchases from NobelKnight sales. Or directly from Paizo and WizKids (as above).
I WISH I had the patience, steady hand, and eyes to paint, but I realized long ago THAT was not happening.
Like so many of us in this thread, I really like the aesthetic of Reaper's stuff. Sadly, they will forever go unpainted.
Right now, I'm focused on slowly picking up Reaper translucent wraiths to fill in a few more undead gaps. And I'm a sucker for the color teal.