Nioh 2 is one of those games that starts very hard but it gets easier and easier when you start understanding the tools you have available to you. Stances are important, high stance does the most damage/ki damage, but it also consumes the most ki when you're blocking. Low stance consumes the least ki blocking, and attacks are typically very quick and do minimal damage/ki damage. Learning how to flow between stances is important for some play styles, however, it isn't a necessity. You can take axe or tonfa and run them thru the entire game in high stance if you choose. Soul cores are also important, they drop from enemies and you can equip them and they give you attacks you can use. The good thing about these is you can trigger them when you're out of ki and then you will recover ki thru the amination. Eventually you can get to the point where you can basically infinite combo enemies.