On a budget, a 4meg fastram card with RTC. Even those cards can fetch silly money these days, but you may be lucky. Obviously you'll need a pcmcia network card, wireless if you like. Then take your choice regarding storage. Personally I have many spare laptop hard drives and you may do as well. Why fork out for a flash storage solution if that is the case...
If you want to play games like AB3D and Gloom Deluxe or flight sims etc then one of Individual Computer's ACA 68020 cards might be a better purchase, as you'll get a bit more cpu power and added bonus of more fastram with pcmcia compatibility.
An A1200 with hard drive and fastram does make a really nice WHDLoad machine.
