Amigamerlin drivers. There's tons a drivers out there actually, Haven't tried them all but so far I've had no problems with the Fastvoodoo2 ones.
If you're really using the right chip, as indicated by the Quake console and still having low fps, you might wanna try the following (in that order):
1) Try using Mesa or WickedGL. They're in one of the fastvoodoo2 4.6 folders.
2) Some other drivers, e.g. Koolsmoky (which is really new) or maybe even the default drivers.
3) How old is your windows install? If its very old- try checking for errors and defragmenting. Scrub your hard disk clean- uninstall any junk.
4) Reinstall your O/S. Windows9x can get really messed up really fast causing all sorts of havoc.
5) Install XP and try your card on it. XP is super stable and lets you narrow down any potential problems without being bugged at the same time by Windows 9x's shittiness. I usually try any new hardware with XP and once I'm familiar with it, only then use some retro O/S. You could install XP, try your card and if it goes well, reinstall win 98 and see if works just as well.