"Bardock" takes place well before the start of Dragon Ball, so, if you're wanting to watch it in story-chronological order, start there followed by "Episode of Bardock", as a spin-off sequel of "Bardock". The Dragon Ball anime can then be watched. (I'm a big fan of chronological order. Although, a lot of the mystery of Dragon Ball will be lost if those are watched first.)
The DB movies are not technically canon but can be generally placed. Some retell the anime episodes, most take place in alternate timelines/realities/dimensions. Some movies are better than others, but if you're wanting to get all the media, "Curse of the Blood Rubies" takes place in place of episodes 1-13 of Dragon Ball, so start the anime then watch it after episode 13.
Watch episode 14 then "Sleeping Princess in Devil's Castle". It approximately retells episodes 14, 15, and 16.
After this movie, watch episodes 14-18, then plug in "Mystical Adventure" before episode 19.
After "Mystical Adventure", watch episodes 19 to 67 then watch "Path to Power". This was the best of the DB movies in my opinion and retells episodes 1 to 67.
Finish out Dragon Ball and watch DBZ: Dead Zone, which takes place between DB and DBZ.
The DBZ movies then break up the anime more so than the DB movies, but, like before, if you want all the media and focus on the minutia of the movies, they can be generally placed, though they will seem out of place in light of the arcs in the anime.
Take this into consideration when you watch DBZ to approximately episode 35 then watch "The World's Strongest" after and so forth.
Watch from episode 36 to 65 then watch "The Tree of Might". Episodes 65 to 74 can be watched then "Lord Slug".
"History of Trunks" takes place in a canon future timeline and needs to be watched after episode 122. This will recap everything he tells Goku in that episode and how he was able to go back in time.
"Cooler's Revenge" will be watched after episode 125. "The Return of Cooler" and "Super Android 13!" are definitely harder to place and have a lot of inconsistencies. Though "Super Android 13!" was released after "The Return of Cooler", it can best be watched after watching episodes 126 to 146. "The Return of Cooler" can then be watched after episode 165.
So as not to interrupt the Cell Games, "DBZ: Broly - The Legendary Super Saiyan" is best watched after episode 193. Turn around and watch episode 194 after, then turn right back around and watch "Bojack Unbound". While it is a lot of back and forth, watch episode 195, then watch "Plan to Eradicate the Saiyans", and then back to episode 196.
Watch to episode 204 then watch "Broly - Second Coming" after it. Watch "Bio-Broly" after watching episode 219. Watch from episode 220 to 253 then watch "Fusion Reborn". This is the best place to watch this movie though there are some strong inconsistencies.
With the advent of DBS, most of "Wrath of the Dragon" has been ret-conned, but going with the alternate timeline excuse, the best time to watch this is after watching episode 287.
Switch back to watch episode 288, then understand that there is a total 10 year time jump from episode 288 to the end of DBZ (episode 291). After episode 288, anything related with DBS takes place.
There is 5 year gap between episodes 288 and 289, so, after watching episode 288, this is when "Yo! Son Goku & His Friends Return", "DBZ: Battle of the Gods", "DB: Resurrection - F", "DB Super", and "DBS: Broly" take place. "Yo! Son Goku" takes place 2 years after Episode 288. These are considered more heavily canon the all the previous movies.
DBZ: BotG and DB:RF is then watched and can be watched in place of Episodes 1 to 27 of DBS. Then, pick up with DBS Episodes 28-131. DBS: Broly is then supposed to take place some time later, but still within that 5 year gap before Episode 289 of DBZ. This Broly movie supposedly ret-cons much, if not all, of the backstory of Goku, Vegeta, Broly, Bardock, and the entire Saiyan race, including many details in the original Dragon Ball, in DBZ, and, of course, in the 3 other Broly movies.
There is also another arc in the DBS manga coming out that might be animated called the "Galactic Patrol Prisoners" arc. This is when it would be watched if animated.
After "DBS: Broly" and/or "The Galactic Patrol Arc", the rest of DBZ can be finished through episode 291.
"DB: GT" can then be watched and, finally, "GT: A Hero's Legacy", which takes place 100 years after the end of GT. Many people do not consider GT canon, but it's fun to watch and see more of your favorite characters after some time has passed. Plus, GT has one of my favorite transformations, and, supposedly, the DBS: Broly movie is canonizing a major aspect of GT.
"Absalom" is fan-made released on YouTube and takes place 12 years in an alternate dimension after "GT: A Hero's Legacy".
"DB Kai" is a redo of DBZ in that it cuts out all of the filler, 'yelling', and does a lot of editing to the original anime. It's more of an 'instead of'. Majority recommend the original over Kai.
