My upgrades are something i battle with. I don't even worry about the instinctual as there few upgrades I would take that give her a second ap. However becoming incorporeal really helps make her tougher. Bloody shears givers her a 5 inch charge. Ikiryo is great but she can be hard to keep around under a determined attack. Bête noire also has a place but only against loads of living or undead.
I used a lot of smaller spirits but feel that the new summoning mechanism does to much damage to them and trying to wait for a 13 is also is a dangerous game to play plus you can only get one seishin out before Karai summons, unless you activate Datsu ba first.I rather start with the most expensive models on the table and try summon the moderate spirits like onryo. Most of the time my games are against the dreamer so anything that messes with my already low Wp messes with my ability to play. Other games are against Marcus, forget about using beasts (shikome) and you need to stand against really tough beasts.
I'm going to be adding izamo, ubume and some drowned, they should give me some more options.