The Hojo, are rich, generally lack access to iron&sand provinces, are way far northwest, which means the Portuguese visit them last and face the Uesugi, so, apart the usual Yari Samurai and Samurai archers you could choose Warrior monks as melee troops (Naginata require armory and hence sand and iron provinces). Yari Cavalry is essential for dealing with the hordes of archers of Uesugi quickly and effectively. Once the Dutch appear around the 1560's you can make a deal with them that does not upset your Buddhist subjects and provides you with muskets. You can invest in an armory in Hitachi or elsewhere after you have dealt with the Uesugi. Generally it is risky for new players to invest in making an armory early in Hitachi as long as the Uesugi holds Mutsu. Once you conquer Mutsu you can go for the armory in Hitachi though.