The single issues that CMX have includes the fantagraphics. so if youdidn't want to buy in volumes, you could just start with single issues
Book 1: The Ronin (1987, Fantagraphics) collects stories from Albedo Anthropomorphics #2, 3, and 4; Usagi Yojimbo: Summer Special #1; The Doomsday Squad #3; and Critters #1, 3, 6, 7, 10, 11, and 14
Book 2: Samurai (1989, Fantagraphics) collects Usagi Yojimbo (vol. 1) #16
Book 3: Wanderer's Road (1989, Fantagraphics) collects Usagi Yojimbo (vol. 1) #712 and a story from Turtle Soup (vol. 1) #1
Book 4: Dragon Bellow Conspiracy (1991, Fantagraphics) collects Usagi Yojimbo (vol. 1) #1318
Book 5: Lone Goat and Kid (1992, Fantagraphics) collects Usagi Yojimbo (vol. 1) #1924
Book 6: Circles (1994, Fantagraphics) collects Usagi Yojimbo (vol. 1) #2531 and a story from Critters #50
Book 7: Gen's Story (1996, Fantagraphics) collects Usagi Yojimbo (vol. 1) #3238 and a story from Critters #38
Book 8: Shades of Death (1997, Dark Horse) collects Usagi Yojimbo (vol. 2) #16 and stories from #78
Book 9: Daisho (1998, Dark Horse) collects Usagi Yojimbo (vol. 2) #712 and 14
Book 10: The Brink of Life and Death (1998, Dark Horse) collects Usagi Yojimbo (vol. 2) #13 and 1516 and Usagi Yojimbo (vol. 3) #16
Book 11: Seasons (1999, Dark Horse) collects Usagi Yojimbo (vol. 3) #712 and Usagi Yojimbo Color Special: Green Persimmon #1, and stories from Usagi Yojimbo Roleplaying Game and The Art of Usagi Yojimbo #1
Book 12: Grasscutter (1999, Dark Horse) collects Usagi Yojimbo (vol. 3) #1322
Book 13: Grey Shadows (2000, Dark Horse) collects Usagi Yojimbo (vol. 3) #2330
Book 14: Demon Mask (2001, Dark Horse) collects Usagi Yojimbo (vol. 3) #3138 and stories from Dark Horse Presents (vol. 1) #140, Dark Horse Presents Annual #3, Wizard magazine #97, Oni Double Feature #11, and Dark Horse Extra #2023
Book 15: Grasscutter II Journey to Atsuta Shrine (2002, Dark Horse) collects Usagi Yojimbo (vol. 3) #3945
Book 16: The Shrouded Moon (2003, Dark Horse) collects Usagi Yojimbo (vol. 3) #4652
Book 17: Duel at Kitanoji (2003, Dark Horse) collects Usagi Yojimbo (vol. 3) #5360
Book 18: Travels with Jotaro (2004, Dark Horse) collects Usagi Yojimbo (vol. 3) #6168
Book 19: Fathers and Sons (2005, Dark Horse) collects Usagi Yojimbo (vol. 3) #6975
Book 20: Glimpses of Death (2006, Dark Horse) collects Usagi Yojimbo (vol. 3) #7682 and a story from Drawing the Line
Book 21: The Mother of Mountains (2007, Dark Horse) collects Usagi Yojimbo (vol. 3) #8389
Book 22: Tomoe's Story (2008, Dark Horse) collects Usagi Yojimbo (vol. 3) #9093 and stories from Usagi Yojimbo Color Special #13
Book 23: Bridge of Tears (2009, Dark Horse) collects Usagi Yojimbo (vol. 3) #94102
Book 24: Return of the Black Soul (2010, Dark Horse) collects Usagi Yojimbo (vol. 3) #103109 and a story from Free Comic Book Day: Star Wars / Dark Horse All Ages #1
Book 25: Fox Hunt (2011, Dark Horse) collects Usagi Yojimbo (vol. 3) #110116 and a story from MySpace Dark Horse Presents #18
Book 26: Traitors of the Earth (2012, Dark Horse) collects Usagi Yojimbo (vol. 3) #117123 and stories from Dark Horse Maverick 2001 #1 and MySpace Dark Horse Presents #35
Book 27: A Town Called Hell (2013, Dark Horse) collects Usagi Yojimbo (vol. 3) #124131
Book 28: Red Scorpion (2014, Dark Horse) collects Usagi Yojimbo (vol. 3) #132138
Book 29: Two Hundred Jizo (2015, Dark Horse) collects Usagi Yojimbo (vol. 3) #139144 and stories from Dark Horse Presents (vol. 2) #7 and 3536
Book 30: Thieves and Spies (2016, Dark Horse) collects Usagi Yojimbo (vol. 3) #145151