Which Ninja you should get is much more depending on your current ninja pool than on your pos 1 desires. Maybe, for the time being you can put something cheap like Fuguki on Pos 1 and link his Mystery with a Chaos Chase. Or you play Sharkbomb Water Main Pos 1. It's hard to tell. For example: if your overall initiative is bad, Shisui will do you no good, because the opponent most likely will get the barriere.

You can get Minatos bond from the bells you get from Shop. Just make sure that you don't buy to many bells before you secure the 1000 keys for cave key rebate (much more important for F2P).