[throwaway81523]

No idea about mruby/C or picoruby but MicroPython is very popular, enough that I'd just settle on it for devices can handle it. It runs nicely in 256k of flash and 32k of ram, on the small adafruit trinket devices. It was shoehorned into the v1 BBC microbit which had 256k of flash and just 16k of ram, but that was apparently painful.

Smaller include Lua and maybe Hedgehog Lisp. Below that there is ulisp but that is sort of a toy. Also there is Javacard and J2ME depending on device size.

Below that you're probably best off forgoing garbage collection and using Forth or a cross compiled language.

[rahil627]

ah yeah, i forgot about Lua! that's def the way to go.