I like to grow plants from seeds. It's a pretty damn cheap hobby. One of my favorite sites for seeds is rareseeds.com
Also ham radio/SDR.
Been learning piano slowly, which is fun.
I've been doing some simple lock picking - tons of fun, pretty cheap. Knot tying is kind of similar and even cheaper.
3d printing is also an amazing hobby.
Also getting into MAME and classic arcade games is cool.