Managing Blood Gauge
The most important thing you're going to learn as Nagoriyuki. Nago's blood gauge fills up as he uses specials and decrease as he lands S normals, HS normals, command grab, and Super. 236K/214K cost 40 blood while 214H, 623H, and 236S cost 90 (command grab cost nothing to use). Landing S or H normals before using a special move will reduce the cost of the following special, especially on hit. For example, 236K cost 40 blood but if you land 5H then cancel into 236K it'll cost roughly 20 instead. The gauge does not fill instantaneously so you will have to maintain a rough idea of where your blood gauge is going to be after using specials.
Each segment of blood gauge reduced the start up of Nago's HS normals and increase their range, allowing for better neutral pokes and better conversions/strings. 5K > 6H works at lvl 1 blood whereas your opponent needs to be crouching for it to work at lvl 0. 2S > 5H works at lvl 2 blood.
Blood Rage
Blood Rage triggers when Nago reaches 3 segments of blood (300 blood total). Your goal is to ever reach this point. During Blood Rage, Nago loses access to all specials and constantly loses HP (even if he gets comboed) but gets the most range on his normals and access to his Zantetsu super. Blood Rage releases a small shockwave that leaves Nago -7 but pushes the opponent away. If the opponent is not in range of this shockwave Nago is punishable from fullscreen and you will likely have to either burst or lose the round right then and there. If you do enter Blood Rage you can either walk back and play defensive until the timer is over or fish for 2H/5H > super to try and kill the opponent. Zantestu is fullscreen so if you have good enough reactions you can punish impatient opponents from almost anywhere. People who know the MU will commit to walking back or downbacking as your health bar drains so you can try to land some 5Hs to deal a bit of chip before hand. It is worth noting that using Zantestu will also end blood rage but the super is also very punishable so be careful about throwing it out.
Neutral
At lvl 0 Blood use Fukyo(236K/214K) and 214H to make your way in. 214 is neutral on block so you can follow up with 5P to contest your opponent's buttons or use other specials to frametrap and punish mashing. 2S is a great tool to handle ground approaches while recovering fast enough to often 5P or 6P air approaches. 236S > 236K is an expensive but powerful way to get in. 236S beats single hit projectiles while also leaving you plus, especially if you use 236K to follow up.
At lvl 1 blood you want to either use Fukyo or 236S to reach lvl 2 and get those big boy normals or play the same way you did at lvl 0 but more be more mindful of the cost of your specials. 2 special moves can easily bring you to lvl 2 or trigger blood rage here.
At lvl 2 you're job is to bully characters using you long range H normals. 5H covers ground space the best but require you to be warry about jump ins and certain low profile moves like I-No's Stroke the Big Tree or Sol's Night Raid Vortex. 2H at blood lvl 2 covers the air while also catching most characters running forward but whiffs on anyone who's crouching/holding down back. Even though you're at lvl 2 don't forget about 2S for checking people at closer range or as a safer way to check ground space, especially since 2S > 5H will now combo. Try to restrict your special move usage to only Fukyo at this lvl. An H normal > Fukyo will reduce the cost of Fukyo considerable so feel free to dash back on block to stay and maintain range or dash forward on hit to keep up the pressure.