You won't need a graphics card if you choose a moth¬erboard with an onboard graphics chipset and when gaming is not your major requirement. But in case you don't have built-in graphics chipset, you will need a graphics card to get display on your monitor.
Entry-level or budget range motherboards won't support high-end graphics cards, so you can opt for either NVIDIA GeForce 8400 series, ATI Radeon 2400 series or the 3000 series. They won't be heavy on your pocket and will give you good Vista performance along with Direct X capability.
For medium range or high-end cards, it is beneficial to go for a motherboard that supports SLI or CrossFire, 'coz invariably with more and more chal¬lenging games being developed, you'll feel the need to have more than one card. So, look for the board which has SLI and CrossFire support.
Also remember, if you are opting for the card having high capa¬bility, then invariably you would need a higher power supply. Do check how much power supply your motherboard can bear before buying an expen¬sive card.