Recommended Measuring Equipment

Understanding how your speakers and subwoofer behave inside your room is key to getting the most out of your system.
Only with measurements, you can confidently make adjustments and set EQs, crossovers, phase, etc.
Luckily measuring equipment got very good and inexpensive over the last few years.

Microphones

miniDSP UMIK-1 - the most commonly used USB microphone

miniDSP UMIK-2 - updated higher-end version of the UMIK-1

Dayton Audio UMM-6 USB - alternative to the popular UMIK-1

Behringer ECM8000 - very popular and inexpensive XLR microphone. Will need 48V phantom power from a microphone preamp - for example Focusrite Scarlett Solo

Earthworks M30 - something of an industry standard and one of the best XLR mics. Not cheap but worth it if you are really serious about measurements. Also needs a high-quality microphone pre-amp

Software

As for software, we recommend the powerful Room EQ Wizard, or in short REW.
Please have a look here:
REW Tutorials
Adjusting the Parametric Equalizer - Pro Tips