I know the title sucks but I have no idea how to say it better in just a few words - sorry for that.

Here is my situation - my current employer is giving every single employee around $1k per year for "self development". It can be almost anything related to IT or self development in general (for example learning foreign language). Some people buy hardware, online courses, licenses for IDEs or for example they simply go to conferences.

Two years ago I bought HTC Vive using this budget because I wanted to play around with VR technology and learn something new. One year ago I bought few Unreal Engine 4 courses (as a followup to the HTC Vive purchase) and few lisp books.

I wonder what would be your ideas for using this budget for self development. I want to be as good software engineer as I can so if you have any suggestions or experiences I would be more than grateful for sharing them with me.

Probably most of the people will start by saying "well... it depends what interests you" so here is a quick summary.

I used to code in C++ (03 and 11) for living for almost 5 years. Currently I am a project leader so I do not work with code anymore. I do it during my free time, mostly in Common Lisp or other Lisp dialects (Scheme when going through SICP or ELisp when trying to contribute to Emacs). I am fascinated by Lisp and I am really interested in this language. Still a newbie though.

I though about spending some money on learning functional programming and lambda calculus. Already bought few books about this topic. I also thought a bit about buying some commercial Lisp implementation but for now Emacs and SLIME works perfectly for me and I am not limited by this setup at all.

As a software engineer maybe you are able to think about your best purchase or self investment so far?

Thanks a lot!