Welcome aboard

My advice would be to expand the A1200 a bit, at the very least, some extra RAM on a trapdoor expansion and an internal hard disk. That would allow you to install the operating system and, using the excellent WHDLoad package (available on aminet), lots of games.
A fairly minimal list of what I'd consider essential (some of which you may already have)
1) Hard disk
2) Kickstart 3.1 ROMs / Workbench 3.1
3) PCMCIA friendly 4MB trapdoor ram expansion or (preferably) a 68030 class accelerator board with as much RAM as it will take.
4) PCMCIA network card and TCP/IP stack (AmiTCP, or if using 3.9 genesis)
5) Beefier power supply (if you are going to use an accelerator card and HD, this is basically a must).
If you already have a LAN, (3) is very useful since you can essentially forget all that tedious transferring of files to floppies to get them installed.
Nice to have, but less than essential IMHO
68040/68060 class accelerator board. Much more grunt than an 030, but there can be a backwards-compatibility trade-off.
Flickerfixer/scandoubler
OS3.5 or 3.9
If money is no object, then a tower conversion and PCI expansion system is a nice way to go.