How to increase signal?

Hello!

I have a 3500 sq ft home, my office is upstairs, husband’s office is downstairs.  We have Xfinity 1200MB service, with gateway. I have the gateway upstairs and we have 6 pods (xfinity extenders),  We still are experiencing low signal throughout the house.  Checked the signal from the ISP to the gateway, great signal, 1200+; but we consistently drop wi-fi with our TV’s.  Should I get a router and bridge it with the gateway so we can stop losing our signal?