Best wifi channel

The short answer to this question would be the one that none of your neighbors are using.  If you're having problems with 2.4Ghz signals I'd suggest experimenting with using channels 1, 6, or 11 to see if any one of them is better than the other.

Depending on your operating system, you can download and install a utility to find the least congested channel in your neighborhood.

Depending on the utility, you basically launch the tool, locate the Channel header and sort by WiFi channels.  The fewer times a channel is listed, the lesser congestion for that channel.  For example, if channel 9 is listed twice, that would be a clearer channel than 1, if channel 1 was listed 12 times.

How to Find The Best WiFi Channel For Your Router on Any Operating System:  http://www.howtogeek.com/197268/how-to-find-the-best-wi-fi-channel-for-your-router-on-any-operating-system/