I'm looking into buying the Nikon D50 (w/ 18-55mm DX lens and 55-200 DX lens), and as a first-time SLR buyer, I have a few questions regarding accessories:

:confused: What basic filters should I get, or should I get them at all?

:confused: Have you had any problems using the SanDisk 2 GB Ultra II SD card?

:confused: Should I invest in a spare battery?

Keep in mind that I am a fairly casual photographer, but I would like to take this hobby of mine to a new level with the D50.

Thanks,
Andrew

I do not use filters for protection, they can induce flare and degrade image quality. Some choose to use them to protect their lens, but a lens hood also helps in this regard. If you do use a filter, always use the lens hood at the same time, and be sure to get a high quality multicoated variant.

As far as spare battery, I find the D50/70 cameras give exceptional battery life, but you can't be too careful especially if you just have it sitting for a while, or if you use the pop up flash a lot.

If it helps at all, I focus on landscape and architectural photography, but sometimes I photograph people.