Romance Dawn : 1-3
Buggy Arc: 4-8
Captain Kuro Arc: 9-17
Don Krieg Arc: 18-30
Arlong Arc: 31-44
Buggy side story: 45-47
Logue town : 48-53 (50,51 filler)
Warship island Arc: 54-60
terrible filler don't bother watching but read spoiler tag
explains that the calm belt surronds the grand line, this basically has no current/wind is unsailable for pirate ships and has larger then normal seakings.
Episode 61 is half filler half canon
Whiskey peak Arc: 62-67
Coby/Helmeppo Side Story: 68-69
Little Garden Arc: 70-77
Drum Island Arc: 78-91
Arabasta Arc: 92-130 (93,98,99,101,102 are filler)
Post Arabasta Arc: 131-135 Basically recap how ppl joined crew
Goat island arc: 136-138 (debatedly the worst filler in the series, definitely don't bother watching)
Rainbow Mist Arc: 139-143 (as far as filler goes this isn't too bad, if you wanna give any filler a chance i'd recommend this one)
Jaya Arc: 144-152
Skypiea Arc: 153-195
G8 Arc: 196-206
Davy Back Fight Arc: 207-219 (213-216 are filler)
Memory Arc: 220-224
Return of foxy: 225-226
226 is mostly filler
Water 7 Arc: 227-263
Enies lobby: 264-312 (279-283 filler about how strawhats joined crew recap, 291-292 and 303)
Post enies lobby arc: 313-325 (317-319 filler)
Ice hunter arc: 326-336
Thriller bark arc : 337-381
Spa island: 382-384
Saboady Archipelago: 385-405
Boss luffy: 406-7 filler
Amazon Lily: 408-421
Impel down: 422-425, 430 and onwards
(426-429 are specials relating to movie 10 which will be written by oda there awful but linked to movie 10 you don't really need to watch them to watch movie 10