I'm working on building my collection up, so that DEC will be used to purchased cards once I have a chance to look at the market.

About 100 of the DEC came from the Splinter Labs Faucet and was gathered over a couple of days. The rest of it come from a blog post from a week ago that did quite well. The post itself, along with in game time probably took 45-60 minutes to write and was the ninth post written. So maybe 10 hours total if you count the time spent setting up all the posts up till that point, the in game time, and time converting assets and purchasing cards.

Most post rewards generate considerably less.