I highly recommend to watch all 4 jojos season, but take note that the story is revolved around of multiple characters with name Jojo.
Generally ppl said the 1st season is the weakest, but i suggest just still with it until you get around good part, because it is important introduction to one of the key character.
1. Phantom Blood (about.. 1/3 of season)
2. Battle Tendency (the rest of 2/3 of season)
3. Stardust Crusader (2 season take note)
4. Diamond is unbreakable (1 long season)
Of course, make sure you watch the latest version of jojo (not the 90s ova one) because simply of Dio's voice actor (if you watch japanese dub of course)
Dont worry about art in 1st season, because the production was kinda experimenting during that 1 i believe.
And be prepared for awesome rides.