Hello Vasanth
It’s good that you see your study for CCNP not just as a way to get a certification but as a practical learning experience for improving your real on-the-job skillset. We’re glad to be of help with the lessons, as well as via the forum responding to questions.
For almost all of the certification requirements for CCNP, using emulators/simulators should cover you for your labbing and study purposes. This includes both free as well as paid options. You can learn more about what’s available at this NetworkLessons note on practice labbing best practices.
Typically emulators are the cheapest solution. Purchasing actual devices is obviously more expensive, and strictly speaking, you don’t need to do so. However, some prefer the “feel” of real devices over a simulated environment.
For equipment that focuses on switching, I suggest you take a look at this lesson:
These are older models, but they should suffice for most of what you need. And the older they are (and if they are EOL too) the cheaper you can find them as used or refurbished equipment.
For routers, take a look at the Cisco 1841, 2801, or 2811. All of these support version 15.X IOS and should do nicely. They too are quite old, so you should find them cheap.
Now if you want to get your hands on an ASA as well, your best bet would be the ASA 5506-X which supports the newer FirePower features.
For wireless, consider the 2504 controller, and at least two 3502i APs, and a single stand-alone AP like the1142.
Now you won’t need the ASA and wireless gear for CCNP, but I just added those in for completion.
I hope this has been helpful!
Laz