I wouldn't worry about filters (not even for protective purposes). A lens hood will give you more protection and have a more noticeable effect on the quality of your shots. There are quite a few Nikkor 50mm's out there, but I believe most of them take 52mm attachments (as you seem to have already deduced).

I would recommend Fuji Superia at ISO 200 as a good starting film. 36 exposures can be had for $2.50 at B&H. It's not the greatest color film ever made, but still very good-- and it's dirt cheap, so you don't have to fret too much if you make a mistake. Kodak Gold is even cheaper (although I've heard some bad things about it's color reproduction). If you want to try lowlight photography, the Superia should hold up better and will be worth the extra .50 cents.

Don't pass up on shooting (and developing) B&W film as well. I dislike B&W C-41 film immensely, and I would say the relatively low cost of buying the basics for home development is more than worth it in quality and control. Honestly, most films are great, although the classic starter film is Kodak Tri-X. My favorite B&W film for landscapes and architecture is Ilford PanF+, although I've never shot it in 35mm.