How to increase FPS in my game with Unity 5.1.3f1

I have a game that I want to Maximize FPS in Unity 5.1.3f

a. I’ve already deleted all lights except the Diffuse Overhead light (sunlight)
b. I’m using the procedural skybox
c. No shadows cast or received on my meshes but in the Lighting Window - the ‘Realtime Computer GI’ box is checked but no other.
d. I use Unity mobile diffuse shader everywhere possible but there are 2 or 3 other shader types I use because of transparency needs or because the make an object look lit in comparison to the surrounding objects.
e. Most textures are already in atlas and are 1024 size. There are not excessive amount of textures.
f. About 250K tris if the Unity stats is to be believed. Will top out at about 350K when all meshes are added that I need. The FPS is consistently 20 - 25 and smoothly playable in the editor but I’d like 30 FPS or more especially since I’ve yet to add the antagonists and other game play.

So what else can I do to increase FPS in my situation?

Oh, also, my protagonist has materials only, no textures so it is using Unity default shaders. I’d like to use diffuse shaders as the FPS is less, but then the materials aren’t used and character is all white. What I easiest way to create textures based on the materials embedded in my protagonist character?

Realtime GI is not used by the mobile diffuse shader so if you have no other materials that uses Realtime GI, you can disable that and switch to fully baked lighting.

Thanks! I need to read about lighting in detail.