Personally i would suggest:
Grap yourself an image of Slackware http://www.slackware.com
Try to configure the system to "Mint Standards", meaning the system feels like a Mint System.
On a Slackware system all packages are "Vanilla". This means the packages/programs are as deliverd by the developper. No interference from a Distro Team.
All packages usually needs to be compiled, there is no dependency check by default.
Slackware teaches you the basics on how a "Linux" system is setup and how flexable it can be. Once you got a hang on Slackware, 98% of all Linux based distros should not be a problem for you to handle or program for.
One word of caution: Slackware is not an easy. You will have to pull up your sleves and learn. Slackware will not kill you, but it will have a bloody good
shot at it