I remember buying Amethyst off-the-shelves as it came out.  I found it to be a very enjoyable comic!  I'd pick up any Showcase collections, but I think this is one title better served by a color reprint.

On a related note, I really enjoyed the Thomas/Colon Arak, Son of Thunder series, too.  I liked that series from beginning to end (post-Colon).

Another DC fantasy series from that same period I'd like to pick up is Arion, Lord of Atlantis.

I'd be happy with color TPBs for all three titles.

My first comic books: Superboy and the Legion of Super Heroes #202 and Kamandi, the Last Boy on Earth #23.  What a great way to start!