But, try and get at least 2 2950 or better switches to practice STP. I have a few cheapo routers (2600, 3600's.). I used to have some 2500's that were good for serial and frame relay, but you can use the GNS3 and Dynamips and get pretty far.
You'll need at least a few half-decent switches and routers if you want physical equipment. I would suggest picking up a few 2950s if you can and a few 2600 series routers. You'll need at least one 2620 or 2621 to do router on a stick. Look at Dynamips, too.