Hi Megabyte,
I would suggest that you get 2 graphics cards - one capable of 640x480 and 256 colours, the other capable of 1153x768 ( or whatever the standard max resolution of the Mac was) and millions of colours. The former will set you back maybe USD 25.- and the latter maybe $60-80. The Radius LeMans card is a good example of the latter. Radius, SuperMac, RasterOps all have good cards. Generally look for something with 24 or Thunder in the name.
In addition, I'd get a 10 mb ethernet card.
If you are feeling flush, you could splash out on an AudioMedia sound card or on a SCSI card. Popular brands include ATTO SiliconExpress series and FWB's Jackhammer. There is also a real risk that that you will overload the NuBus bus with too much data.
Speaking as someone who probably shouldn't be allowed on eBay, if you aren't going to use it then don't get it. I have a Fibre Channel card that I'm to get working...
Once you have a graphics card, get the board recapped (the onboard SCSI in my IIfx has gone, for example), invest in new PRAM batteries and buy at least 8MB of RAM. You don't need any more than 32MB and 8x4MB is not difficult to find.
Finally, get yourself a SCSI2SD card or one of BigMessoWires' cards to replace your 30 year-old SCSI drive and Mac II will be a lot quieter.
I hope that helps,
aa