Personally I pick one new thing per personal project and leverage my skills on the rest. If I go too far into the new things then I get bored or flummoxed with say "buck build system" and "learn kotlin" in the same project, and never actually make progress.

I think this is why I bounced off of react 4 times before sticking, too many things to learn at once. Then again I bounced off of antlr 4 times and only really got it to stick because it was a work need, and antlr is the only new tool in that chain.