It really depends on your work environment.
If you have access to Cisco gear at work, it's a luxury.
If you don't, you really need a physical lab. There's no end to the weird issues and problems that I ran into with even nice simulators.
Of course, the above advice is considering that you're intending to go beyond the CCNA and/or get specialized certs. If you're just getting your CCNA and not going further into certification you could probably get by with simulators.
Note: When you do take the CCNA, take the combined test, not the CCENT and separate second test.
I got the CCNA just using GNS3, so I can confirm this is sufficient. You can add switch modules to routers which is enough to get the CCNA job done for practice.
Beyond that you should at least get switches, since GNS3 doesn't emulate Cisco Switches well. Personally I got switches and routers...then I got a job where 99% of our equipment is Juniper, so there you go.
One note, however, having Cisco Equipment at work is helpful for learning basic commands, but isn't helpful for studying unless you have equipment that you can reconfigure however you want.
Regarding lab kits, if you want to go all physical devices, then you'll need 3 routers. Make sure they have IOS 12+. You need 3 for properly practicing NAT and Routing Protocols, though GNS3 is arguably better since you can setup more complicated networks. A lot of people say you just need 2 switches, but I really think 3 is helpful for messing around with STP. However, not all routers and switches can do everything needed. If you plan on getting a CCNP, then you might as well spend a little extra and make sure you are getting routers and switches that can cover everything in there.