ASA 100 and 400 are the two most popular film speeds - 100 for bright days and 400 for action and varied light (almost everything else).
ASA 200 was conceived as a "universal" film for the amateur market and usually had compromises that I didn't like.
I haven't bought film in such a long time I'm not sure what's available any more - no more Kodachrome 25 I know...
You can extend film's life by storing it in a plastic zip closure bag in the freezer - just let it thaw for a day before you use it.
Shoot some Fuji slide film to begin with and try some black and white Ilford 100. Tripods are your friend with film.
Luminous Landscape is a good site:
http://www.luminous-landscape.com/forum/index.php?topic=38161.0
I've spent a bunch of money at KEH over the years and never been disappointed - they are good folks to buy from.
As everyone says their rating system is very conservative - Excellent generally means its like new.