Not the person above, but I'd recommend learning APL first. Arthur Whitney (the author of k and q) got started programming by his father and Ken Iverson (the inventor of APL) being friends, and Iverson giving him live demos of APL. Iverson has a lot of amazing resources for learning J (APL's successor) and APL, and learning it will teach you how to be more productive in q, k, J, APL and more!
This is the arthurese micro APL implementation, which inspired the J implementation - although IIRC the design for J was already well on its way at the time (and indeed, Iverson did not consider J a new language, but rather an improved APL dialect, so you could say the design goes back to 1956...)
It likely also formed a draft for A/A+ which Arthur did at Morgan Stanley (open sourced at aplusdev.org, but unmaintained and rotting theese days) - which themselves led to the creation of K.
