The onboard video on the Quadra 700 isn't too bad. Upgrading the VRAM will give you some color depth on larger monitors. As for NuBus video cards, many were made some were great, others were nothing more than a duplication of the hardware on the motherboard.
Rather than spend money on a video card, actually use the machine for web surfing, and if the color and resolution are not acceptable, go out and find an old Radius Rocket or other card from that era.
Of course, sticking with the onboard video will prevent any need for drivers, etc.