Best Spells/ACF's to Complement a Ninja [PF]

[P.F.]

A friend is playing a ninja in an upcoming game. He is a slightly better optimizer than I. He played the rogue to my ninja in a previous campaign, and probably his ninja will be tapped for that party role. Having played the ninja in a previous adventure and fount it lacking, I am considering a CoDzilla or Bard who can best experience some vicarious satisfaction in making the ninja more effective both in scouting and combat.

We are only level 4, so there won't be terribly much either way. Pathfinder only, at most I could get away with one third-party spell/feat/ACF which is not itself overpowered, subject to DM approval (as in turn in your character sheets so I can approve them and make copies).

What is the best synnergy caster to pair off with a skillmonkey ninja?

[Florian]

Synergy well with a Ninja? Possibly Skald. Rage him up when he goes TWFing.

[Psyren]

What is the best synnergy caster to pair off with a skillmonkey ninja?

I would go with Mesmerist. (http://www.d20pfsrd.com/occult-adventures/occult-classes/mesmerist) You can implant helpful hypnotic buffs in his mind that he can activate while he is scouting or fighting, e.g. Chain of Eyes, Spectral Smoke or False Flanker. You can also sneak alongside him, and do so much more easily than a Bard or Skald because all of your magic is auto-silenced, e.g. if you end up in a tricky situation you can turn invisible or put sentries to sleep without alerting them.

Alternatively, if your group needs a tank, I'd consider the Spiritualist, and buffing up your Phantom to be a strong flanking partner while you support both of them with psychic magic.