Thanks for the tip, disabling fog fixed Gothic on my graphics card. My current platform is a Duron 1800MHz and a motherboard with a KT333 chipset and 512MB DDR RAM (I'll probably upgrade to an Athlon XP 3000 soon). The motherboard is a Shuttle AK35GTRv2.2. I think it's quite powerful with a universal AGP slot. I'm using Win98SE and your driver (the version is from a few months ago, I'll update later).
Getting back to the game, I used the "b frate b" code, which displays the fps count and the number of triangles on the screen in game. I ran around the Old Camp (a challenging location) and monitored the fps situation. The game engine automatically limits the fps to ~20 fps when pressing the movement key, this is normal for Gothic without community patches. I'm using the full 1.08k version of the game from the CD.
After testing, my conclusion is that the stock Rage Pro Turbo 8MB is a bit too slow for comfortable gameplay. When I set minimum settings, with the sky disabled and the view distance set to 20% the frame rate isn't too bad, but I think the game loses too much, and I don't recommend experiencing this RPG game this way.
The situation changed significantly when I overclocked the card to 105MHz on the core and 115MHz on the memory with Ati Tweaker.
Now, playable settings are: 640x480 16-bit, texture and model bars set to 20-25%, view distance set to 40%, and sky effects enabled. This may not sound like a pleasant experience, but in my opinion (I know the game very well and have run it on many different machines), playing it this way is enjoyable and gives it a more "retro" feel than on newer systems, I don't see a problem with playing the entire game this way.
In summary, for a Rage Pro 8MB, I'd say Gothic is playable on low settings (not the lowest), but only after adding core cooler and overclocking the card.