There’s a couple of different paths you can take.
First, you can buy an entire home lab that has everything you need for CCIE, CCNP, or CCNA studies. Those packages are usually quite expensive, but they will include everything you need.
Second, you can buy it all in increments off of eBay, Craigslist, and through word of mouth. The benefit of doing it this way is that it will be cheaper. The downside is that you have to know exactly what you need.
For a CCNA lab, you can probably get by with a couple of switches and a few routers. I recommend you look at the 3550 for the switch and the 2600′s for the routers.