Honestly, you are digging too deep into 1 team without taking other ninja replacements into consideration

I would recommend the Shisui team but kick out Hinata and put Iruka on pos2

So:

Fire Main - Shisui - x

Anbu Itachi - Iruka - x

x- x- x

About general question as to which expensive ninja you should buy:

I would highly recommend Shisui and Masked Man , you won't regret getting those 2 for sure since they are useful in so many teams. (other ninjas you wrote about are too situational and much harder to make teams with, except Minatos maybe)