Go for a Blizzard 1230 50Mhz or similar. The Blizzard is probably the best because it has a very fast memory controller and is ultra compatible. Add 32mb to the accelerator card.
Make sure you have Kickstart 3.1 so that you can at least enjoy Workbench 3.1.
A 2.5" Laptop HD or a CF and IDE adapter with at least 4gb so that you can install your OS, WHDLOAD and games and any other applications you may want to use.
A PCMCIA CF adapter is really usefull for transferring files to and from your pc and they are cheap.
If you intend on using OS3.9 i would really recomend a Scandoubler as the older 1084 and Philips monitors do not support any decent resolutions without horrible interlace.
Also, register your copy of WHDload so that you won't have that annoying delay of the shareware version. Its cheap to register and worth it.