T slots/AA is pretty limited for Agano, I'd just add torp tubes to those slots for blitz/ASW.

As for the 6" on R slots, feel free to use the trips, they will be the most effective guns Agano has access to. AA with those if you must.

Take as many scouts as you can and scout for your team. Agano can pack in more scouts than most, if not all, no CV type ships. Useful in GB.

Aganooooo
I used to hate that ship... and i still hate it.
Not enough R slots to do serious AA or damage (6.1' A kinda work but i doubt you have the gunners for it).
And often will get beaten in a board to board fight with some DD.

Allright so agano it is...
Blitz - Use 7'9" in blitz and stay away agano is just too fragile for any straight to the face combat.
or
GB - Use 6'1" and stay near BBs doing AA and shooting at ships that get close enough.

An interesting way to play it is to front gun it with the triple 6"Ds, perhaps heavy shells, as a cruiser your job is to engage smaller incoming ships, so torps will help in that aspect, if you wish to keep that rear gunner active, try a HH in the rear R slot ( switch between rear and front guns as you see fit ) i still recommend remodeling at some point, rocking the oyodo with scouts can be handy for your team.

oyodo + scouts + mines > agano :D

If your gunners are so-so I'd suggest the 3x6,1N as they have a nice accuracy revision.

Otherwise go for the 2x7,9 that gives both good range and punch.

The Agano has 3 support slots with 5 on ship slots ( gunners 2 T slot and BO)