Hi there,
I am new to digital painting and am very motivated to learn concept art. I used to play around with my Wacom tablet a few years back before university and these days use an X220T. I am an engineering student and so, I am not studying to be a professional in the field of concept art. My question is, given my situation, is it still worth subscribing to a DT membership? Or is self-learning the better way to go about my goals? Any feedback would be appreciated. Thanks! 
If your painting go with the gnomon. Just try it for a month. I think it’s 60 bucks or so. Really great material there.
Subscription CG resource pipelines are actually one and the same in reference to self taught options currently available, I think in your specific circumstance non-commercial application concept art, in my honest opinion would be most beneficial & worthwhile in respect to an effective plus efficient progression as a digital artist.
In due course however its entirely dependant as to graphical fidelity and/or art style of output at the end of the day you want to achieve, not forgetting in addition to funding the hobby as opposed to the host of freebie tutorials via youtube or the plethora of artist hubs such as ConceptArt.org delivered instruction in either video, text or screencap’ed format.
That said for me quality is the litmus test so invariably I tend to lean towards sub-fee avenues for CGI teaching on occasion eg: The Gnomon Workshop and since my primary box modeling app is the current Blender 2.71 iteration CGMasters amongst others.
Cheers 