Ideally you want at least 2 routers and 2 switches, but 3 of each is better. Of course more is always better, but the return on investment isn't that great after 3. For switches, the sweet spot as far as price/features is the 2950, which you can pick up for less than $50 on eBay. As far as routers, what you have is sufficient as long as there is enough RAM and Flash in them to run a decent enough IOS verison. You want at least IOS 12.2.
If you can't/won't afford any further equipment, download GNS3 (a free Cisco router emulator) and http://www.freeccnaworkbook.com
. It will walk you through downloading and setting up GNS3 and then take you through exercises that will cover all of the CCNA exam topics. You can also get free remote access to a full lab at http://packetlife.net/
and at http://www.stubarea.net