How can I get IP connectivity on my non calling tablet without using WiFi? Actually my issue is that I want to use my tablet as a second display over USB. I have used team-viewer over WiFi and it works fine, but since it is over WiFi, there is significant lag which defeats the purpose of a second monitor.

So, I wanted to know whether I can get IP (Layer 3) connectivity with a USB cable and some app (maybe) on my WiFi only tablet. I don't have a USB tethering option in my settings. I also have enabled USB debugging mode.

I can easily do this on my phone which has "USB tethering option".
If your device supports USB OTG, then you should look into a wired Ethernet adapter.  Depending on the specifics of your tablet, if it works, this is the best solution.  Android SE, example how-to, XDA, example cable to let you charge and Ethernet (eBay).

If you're not rooted, or don't have USB OTG, the next best option is to buy another WAP of the fastest type of WiFi that your table support and put it near the tablet.  If you normally use 2.4Ghz Wifi, then get one that's only 5Ghz, assuming your tablet supports 5Ghz.  A different band will reduce interference and let the tablet and WAP use their full speed.