Unfortunately, you will have to watch the first 5 seasons in sequence to make any sense of the final season.
However, they do have an hour “recap” at 8pm, that may help, but I have doubts...and I’m not being glib. It’s just very complicated from the science to the mythology and philosophy to the “ships (relationships).
Give it a try and if you like it find someone who has the other seasons on DVD.
I never watched a single episode until after the 4th season when a friend recommended it and gave me season 1 and 2. Bought 3 and 4 and was up to speed for the 5th.
Hulu.com has/had the entire 5 seasons.