A common route order I see is the following:
Carl, Leo, Route 65, TJ, Flynn and end on Jenna.
I used this order myself and enjoyed it. This is also the order everything came out in from my understanding.
You can tweak the order a bit, like doing Leo first or swapping around TJ and Flynn, but I suggest that you save TJ and Flynn for your 3rd and 4th playthroughs and do Jenna last.
Route 65 is a prequel to Echo with the same cast, but it should be played after you do Leo’s route for maximum emotional impact in my opinion.
After you finish Echo you should be good to go with Arches (Sequel) or The Smoke Room (Prequel). You should probably finish Echo first before going to either of these, but I was introduced to the series with Build 2 of Arches and don’t feel like too much was spoiled.
Here is the timeline you asked for as well:
Echo takes place during Spring Break of 2015 (Mid to late March).
Route 65 is a prequel to Echo with the same cast set on November 1st, 2008, when the cast is in High School.
Arches is a sequel with a new cast of characters that takes place after the events of Echo in 2020, at some point before Lockdown (Likely February or Early March).
The Smoke Room is a prequel with its own cast set in the town of Echo, but in 1915.
Technically you could play the game chronologically, however, it would be better to play starting with Echo in my opinion and sandwiching in Route 65 after you complete one or two routes in Echo.
Hope you enjoy the read!