There are some good traders on ET but an even larger number of the clueless who none the less don't lack for opinions. Everybody sees things differently, my advice would be to spend many hours watching price development. Draw channels if that's what you want to explore...patterns of price behavior will begin to emerge over time. Ultimately, you will have to trade what you see and not what someone else see's or claims to see.
Regarding trading channels; it can be quite a vast concept. First off; you're going to need to find some objective procedure for drawing channels as best as you're able. Remove as much subjectivity as possible or you will get nowhere.
The most commonly advocated method for beginners is to enter into a trend that is already existing. Every channel has a slope. The direction of the slope is the dominant direction of the trend. There will be non-dominant movement against the trend slope intermittently as higher highs or lower lows are made.
So you need to find a way to qualify the dominant direction of a trend; wait for non-dominant; and then enter into the return to dominance. Here are some basic entries of this type from ES yesterday. The dominant direction was qualified; non-dominant movement ran it's course, and then price began translating once again in the dominant direction. There are additional considerations such as exits and risk metrics for you to develop; but I'd recommend focusing on one thing at a time and making iterative refinements when you discover them.
If you study this example you may realize these entries were triggered by objective criteria and not merely cherry picked with the benefit of hindsight which is the assumption most people usually jump to.

I hate to be a dick, and maybe I'm wrong, but from my point of view, what you draw is highly hindsight laden. Take the first trendline you have, the downslopping one that is magenta. It should be extended, as I have drawn via the red line, and it perfectly hits point C on my version of your chart. Therefore, there is no reason for you to stop drawing in this trendline, except if you knew that an uptrend was coming.I draw in the channels on multiple levels of resolution as soon as there is sufficient data to do so. Once there are two points to create a right trendline, I clone the RTL and place it on the point of maximum volatility between "P1" and "P3". I adjust my trend-lines as future data forms and fan or steepen them according to certain criteria until they reach "completion" and then I start a new channel in the opposite direction. Here's what my chart would've looked like in RT at the first short entry.
The method is very nuanced. Forum users Jack Hershey and Spydertrader wrote much about this method of drawing channels and related concepts over the years; I'm sure you will eventually come across their works or references to it if you poke around here long enough.
However, the purpose of my post was not particularly to get into the mechanics my own trend channel drawing. Rather I wanted to speak to the underlying principles on how to begin exploring trading with channels. As speedo says, before anything else a copious amount of screen time is really necessary to make progress with this stuff. I merely wanted to leave you with a few other pointers that I believe are helpful to someone starting out on this path. Best of luck.
1. Screen Time
2. Objective Criteria for Annotations
3. Specialize in one specific trade at first [i.e. return to dominance]
4. A consistent set of rules for all trading actions
5. Don't scatter your focus
I'm a price action trader and I'm building a system over channels but I found them very subjective and confusing.