I started out in Minecraft classic - the free in-browser version of Minecraft where the only gamemode is creative and you get an extremely limited amount of blocks to build in (
http://minecraft.gamepedia.com/Data_values/Classic). The first Minecraft classic server that I played on made you build for ranks. Higher quality builds means higher ranks, like how some creative servers are formatted today.
Here's an example of a build I did on classic:
http://i.imgur.com/QKHBd.jpg
I would say that's the start of when I got interested in building something other than square boxes.
When I got the full version of Minecraft I played in survival for a while building wood and dirt boxes to survive in, but then I started watching Minecraft videos on Youtube - gameplays, walk-throughs, and
timelapses.
FyreUK (sad to see them go, but it's actually pretty funny that I mess around with some of their builders now) was was an insanely huge inspiration for me in creative building, and mostly the main reason that I started to strive in improving my building skills again. I tried to build villages or big builds like theirs, in order to make timelapses by myself.
Old timelapse example (actually had to dig quiet deep for this):
But the quality of my builds in those timelapses never satisfied me, I always compared my builds to the "big" teams, I kept trying to make my builds better, studying the detailing and structure from other builders and teams, mainly FyreUK.
During this time, I joined a few creative servers that made you build for ranks, lost most of my interests in making timelapses (after learning how they're really made), and vastly improved my building skills after interacting with many other skilled builders.
Example of my building skills around this time:
http://i.imgur.com/y43EWQj.jpg
After a while, when my building skills were barely above average, a few friends asked me for help in becoming a builder for their server. That's when I realized that building can be for something other than creative fun (but it mostly is creative fun).
It was only a couple months ago when I actually applied to build teams, I had been building alone the whole time since I never found anyone that was as interested in building as I was, but that's changed now.
I used to freerun (yes, that is me, circa 2012)