Wi-Fi channel selection will vary widely depending on your environment.  In general, it is best to leave the channel at Auto, since the router/gateway has algorithms to evaluate your environment and select the best channel to use at the time.  However, if you are experiencing interference and would like to set your channels manually, you should start with:

2.4GHz: channels 1, 6 and 11 are non-overlapping channels and will be least likely to interfere with each other.

5GHz:  start with channel 149 and above if you do not have 6GHz Wi-Fi 6E devices.  If you have Wi-Fi 6E devices, start with channel 36.  Some products will support channels 52-64 and 100-140, which are called DFS channels.  These channels will be cleaner with less interference, however, since they share the space with radars, if you live nearby an airport, or have weather radars close to you, the router will be kicked off these channels when it detects radar activities and you may be better off selecting a non-DFS channel

6GHz:  Stay with channels marked as Primary Scan Channel (PSC).  Avoid using channels 5 and 37 as these channels are closer to the 5GHz band and may cause issues with your 5GHz devices.