ARROW (Flash, Legends,Supergirl)
You should start by watching the first two seasons of arrow. Now, when you start arrow season 3, start the flash season 1 at the same time.
After you start watching arrow season 4 and the flash season 2 you can start to watch supergirl but it's optional(YOU DONT REALLY HAVE TO WATCH SUPERGIRL TO BE ABLE TO WATCH THE REST OF THEM).
After arrow season 4 episode 10 and the flash season 2 episode 10 you can start watching Legends Of Tomorrow.
Now when you finished watching all of them you can watch them by their air date as they come out.(KEEP IN MIND YOU ARE WATCHING THEM AT THE SAME TIME. )
