Mid-Grade Equips/Xtals??

Weapon:

Resolve Rod is okay for now, but you need to either farm up Princely Rod, and start upgrading it yourself, or buy Tsarita Rod (Final upgrade from Princely Rod). It is one of the best universal rods.
Staff of Dawn also works well but it is quite expensive since it is prod item.

Xtal wise, besides Sauro2, you can try getting cheaper Gerust or Fiona xtals

Armors:

Struggler up is already good, just needs an xtal. You could try finding Medona but price wise it might just as easy to try to save for Fred Xtal.

Additional:

Definitely ditch Monty, it doesn't help your Bishop in anything really.
Taenia Beret is good overall, not hard to upgrade.
Light Bulb is also a good one. A bit harder to upgrade.
Fallen Angel Wing is a great add, but expensive to get.

Xtal currently would be best to use Dunkelis II , it is pretty cheap at the moment because of the Anniversary Event. 

Special:

Your spec is alright. I personally went with Wasteland Spring Water, ns at first.
If you ever get 1s, then you can even put False Grecia on it, because Bishop's MP cost is so good. 
Otherwise save for Agira Jarma , or like blackghost mentioned, farm Flash of Day xtal 


Overall your set isn't bad already, You have good light magic equipment. 

Also go for a white maid headdress. And when you get apostilia access I suggest getting a flash of day al as well. Its Xtrade tho. Zweig shield might also help?

I'm a paladin so I also use Light magic stuff to enhance my holy thrust damage and other stuff to enhance my one heal skill.

Zweig shield has heal reward up by vit, highest rate cut in game and has a VIT+1-15 bonus (depending on upgrade lvl).