[richardknop]

Probably invest in yourself.

1) Buy books about programming / machine learning / etc and read them. Add some online courses to get some practical knowledge.

2) Flight ticket & hotel to go to some interesting tech conference and do some networking (this can lead to opportunities later).

3) You could also buy some new hardware for development, if your current gear is getting old and clunky. This also is good long term investment.

[jackgolding]

I agree. If you are in the first 7 years of your career especially this will do wonders for you.