Paul’s 3D printed LowSpec instrument is giving very good performance and is very cost effective.
https://www.thingiverse.com/thing:2455390
Well supported on the
https://groups.io/g/astronomicalspectroscopy
Many of us use BASS Project for Spectral processing. It has a comprehensive manual and well supported.
https://groups.io/g/BassSpectro
Remember if you build/buy a spectrograph it can also be used with a suitable scope as a spectroheliograph (SHG). Then you can safely image the solar disk at any wavelength CaK, Mg, Fe, Na, any of the hydrogen Balmer lines etc. etc.
Fulvio's good eBook on his SHGs is worth reading.
English version here:
http://www.lightfrominfinity.org/Libro% ... graphy.pdf
There are further details on the
https://groups.io/g/astronomicalspectroscopy