Ask HN: Best stack for a newbie progressing beyond basics?

A friend's son is learning programming and he's asking me for ideas. He's nearing 18 and progressed via Minecraft to some python and PHP on a Raspberry Pi, and his PC now has Ubuntu. Not quite sure how he got to php, but he's had lots of fun messing with sensors, cameras and web pages. Everything is entirely self-taught so far.

What stack would you suggest that will give him some good habits, and develop the interest? To be clear, he's not trying to become employable, just to learn all the web things! Jobs may follow later of course.

Ruby would get him producing quickly, Clojure might be better for all round thinking, but is it too confusing or offputting to a beginner? I want to direct away from PHP as there's too many bad habits disguised as tutorials out there. Front end I have even less idea of best suggestion of framework for him.

It's such a long time since I was thinking as a beginner, before I knew of OO and functional, so I'm not sure where to go with this or best order to present things. The last thing I want to do is put him off. Ideas?