I've found it confusing how to optimize my chat too. Here's how I deal with it as for now: I continuously leave and rejoin channels according to what subjects I want to keep track of, using the Local channel for the reading. When I want to write something, i go to the desired channel, send the message and go back to Local to continue reading. As example, I sometimes activate the channel from my country, sometimes the Help channel (when I have some spare time to answer questions from players or when I get my own questions), I personally don't get into trade chat often and sometimes I stick with only the All chat. The downside is that you can't read anything that has been sad before you rejoin a channel. Anyway, as the way the chat is designed right now it's important for you to manage the priority of what you want to read. Also, make use of the color system.
Regardless of the advices I gave you, this is indeed a good suggestion. It would be awesome to have more tools on optimizing the in-game chat to suit your needs. Thank you for your post and I hope mine has helped.