For your purposes performance should not matter.
I'll list some common network cards.

ISA -> NE2000 compatible, 3Com 3C509 (containing TP in the suffix)
PCI -> RTL 8029A based (10 MBit/s), RTL 8139 based (100 MBit/s) (from DOS up to Windows 10), 3Com 3C905C-TX (100 MBit/s)

I personally prefer setting my ISA NE2000 compatible cards to IRQ 10 and port 280 so that I easily can swap them.

The fun thing is is that even the newer Intel based cards have DOS drivers still available. Not sure of the memory footprint but I was looking up stuff a while back and saw that Intel had NDIS drivers still available for DOS.
https://downloadcenter.intel.com/download/291 … ers-for-MS-DOS-

Here is a link to the web page that has DOS packet drivers for the 100Mb Intel NICs:
http://web.archive.org/web/20190119091806/htt … www.crynwr.com/

Drivers are the most important consideration, just about any 100MB card will have drivers for dos gaming and Win98 as long as you can find the driver disk.
Popular choices for PCI are the 3Com 3C905 series and Intel Pro 100 series which are a bit lighter on resources or CPU cycles.
Realtek RTL 8139 get a bad reputation as they do use a bit more in resources but I don't mind them It's not like you notice and drivers exist for just about any OS ever created.

None of the above should cost much, truth is not much demand for 100mb cards outside retro computing so don't fall for the high priced buy it now listings.

ISA is bit harder to find
NE2000 compatible is like saying Sound Blaster compatible. Not all cards compatibility are equal which can be annoying but as long as you have the driver disk you should be ok.
Don't bother trying to find 100MB isa cards, They do exist but rare and expensive and on a PC without PCI then good chance it's not going to be able to take advantage of 100MB anyway.

For the 3COM cards, I used to use the ones that had "Parallel Tasking" labeled chips. They seemed to have the highest performance and lowest resource usage of any card I tried back in the day. Newer cards might be better though.

For ISA, I'd definitely go with the 3com cards because they have good driver support and usually just work.
For PCI, I agree with the statements above. I try to stick with 3com and Intel, but haven't had any issues with Realtek either. Actually, the first Ethernet card I ever bought (for the sole purpose of attending a LAN party some time around 1999 or 2000) had a Realtek 8029A chipset, so I am a little bit nostalgic about that one. Even though 100 MBit and the RTL8139 chipset were already around, the people at that LAN party were still using 10base2 and BNC cabling so I had to get the older 8029A 😉