I just started taping this summer and it has quickly become a huge source of joy and passion in my life. Here's the first show I recorded, by Jazz Is Phish: https://archive.org/details/jip2019-08-20.aud.flac16

For this recording, I used a pair of microphones that are frequently recommended to new tapers: the Audio-Technica ATU853 cardioids. Sound Professionals calls them SP-CMC-4U according to their internal product numbering system. They're not perfect, but they're a great value (in terms of sound quality per dollar) and easy to set up. Select the "low-sensitivity" option to make sure that they'll be fine in loud concerts (i.e. anything that's amplified... microphones can have a very different conception of loudness than our ears and can mess up when the sound from the PA hits them). Here's the link: https://www.soundprofessionals.com/cgi-bin/gold/item/SP-CMC-4U

You can still get usable recordings using the internal mics on a handheld recorder, and if you're the only taper there, your contributions to the music community will still be valued. But if you're interested in maximizing your impact, or if you like spending lots of time and money on dialing in the sound you like, you should consider getting a full rig.

Church Audio (mentioned above) makes great cheap gear, and I use a lot of his equipment, but it's one guy and the wait time can be months. However, you can sometimes find his gear for sale (used) through the Taperssection website (also mentioned above). There's currently a pair of his cardioids for sale if you move quickly — I can't link to that page because you need to sign up for the forum to view it, but you're looking for CA-14s.

The recording deck I used for that JIP show is awesome because (to simplify a bit) it has a beefier amplifier than most decks of that size. This means that many people use it without a battery box or a pre-amp in between the deck and the mics, which you typically need for louder shows (there's a bunch of acoustic physics involved there that I'll skip but you should look up). However, I just checked and it looks Sound Professionals are no longer selling it (I think Marantz stopped making it, I was surprised I was able to get one this summer). You could also look into the new Sony PCM-A10, which has been generating a lot of interest because it's super tiny.

Also, if you get the AT mics I mentioned above, you'll need to put them on something! My starting-out setup was a Manfrotto Nano stand (what we call "mic stands" are almost always stands for lighting equipment, weirdly) and this package from Sound Professionals which includes a "T-bar" and two mic mounts that fit the 853s: https://www.soundprofessionals.com/cgi-bin/gold/item/SP-DTS-11 And I think you need an adapter because the T-bar has a different thread situation than the top of the stand (I forget which one).

I'm happy to share anything else that I've learned, but again, Taperssection is where the real wisdom lies — if you have specific questions, I would Google your question and add "taperssection" at the end of the query to see if anything comes up.