What video card would be compatable with a insignia computer model d300?

I would recommend any of the Nvidia or ATI video cards that come in the PCI format. Your computer only has PCI slots. These are the older slot types, so your options will be limited for brand new cards, but there's still plenty out there. As long as the slot type is PCI and the chipset is a major manufacturer, it should work with no problem. Do NOT get any video card that says "PCI Express" or "PCI-X" - they won't fit.

Video cards for desktop computers are available in PCI and AGP bus types. The latest cards are AGP type, they are faster and better because the AGP expansion slot is designed for video/graphics cards.
The range of graphic card is large and in price, because the graphics cards capabilities depend upon the graphics capability (eg rendering performance), graphics processor and size of video RAM etc.
To determine which video card you should buy depends upon how much money you want to spend and the video card performance to match the various graphics requirements of your programs. For example, if you play games that have realistic images and smooth actions then you need a high performance AGP video card with high CPU and rendering performance with 2Gb video RAM or more RAM.
Speak to your friendly computer shop to check what is available, or check the Internet - do a Google search on high performance video cards etc.