Which OBD II diagnostic tool?

Gentlemen:

I have been having intermittent problems with our 97. One code indicated that it had a bad EGR; I replaced it but still have problems. Since I do not have the diagnostic tool, what would you recommend buying? I'd like to stay under $100 if possible, but have it be quite versatile.

Thanks in advance,
Jack C.

Codes usually do not mean a part should be replaced they are just a starting point for addt'l diagnosis. A scanner cannot really be bought for $100 that will provide live info, maybe 200, such as a basic Actron.