
pretty sure it's Sword Art Online - Aincrad: http://www.mangago.zone/read-manga/sword_art_online_aincrad/

Then it goes:
Fairy Dance: http://www.mangago.zone/read-manga/sword_art_online_fairy_dance/
Phantom Bullet: Not on mangago, but you can buy it on Amazon or watch the anime
Calibur: Not on mangago, but you can buy it somewhere I think
Mother's Rosario: Not on mangago, but it's probably on Amazon
Alicization: http://www.mangago.zone/read-manga/sword_art_online_alicization/
Sword Art Online - Girls Ops: http://www.mangago.zone/read-manga/sword_art_online_girls_ops/ (this one is like a side story about girls)
Progressive: http://www.mangago.zone/read-manga/sword_art_online_progressive/
Alternative Gun Gale Online: http://www.mangago.zone/read-manga/sword_art_online_alternative_gun_gale_online/
Kirito's Thousand and One Night Story: Not on mangago, it's somewhere else (short side story)
Hollow Realization: http://www.mangago.zone/read-manga/sword_art_online_hollow_realization/
Ordinal Scale: http://www.mangago.zone/read-manga/sword_art_online_ordinal_scale/

I just looked over it and even I feel that it's confusing lol so I wrote explanations:
Fairy Dance - part of the main storyline, right after Aincrad
Phantom Bullet - part of the main storyline, right after Fairy Dance
Calibur - side story set in the game in Fairy Dance
Mother's Rosario - side story set in New Aincrad (this is something that happened at the end of Fairy Dance)
Alicization - part of the main storyline, right after Phantom Bullet
Girls Ops - spin-off based on some female characters in the series
Progressive - retelling of Aincrad
Alternative Gun Gale Online - spin-off set in Gun Gale Online, Phantom Bullet's game with new characters (no Kirito, Asuna, etc.)
Kirito's Thousand and One Night Story - same as what I wrote in parantheses
Hollow Realization - based on the actual game, with a new VRMMO setting
Ordinal Scale - adaption of the movie, set after Mother's Rosario and before Alicization, new game
can any one tell me which sword on line is the first on to read there's to many and its giving me a headache. (๑•ㅂ•)و✧