take a look at:
http://amiga1200.deviantart.com/its got a lot of info useful for newbies
basicly id agree that a 1200 hd is a good way to go.
Im in the process of souping up my A1200
things you might want:
HDD
CD drive (scsi or ide)
compact Flash reader/writer
accelerator and 3.1 ROMs
AmigaOS 3.9