Hi,
the optimization really are on your content first:
-- use mobile friendly shaders
-- use very optimized and low poly meshes
-- don't use fancy camera effects
-- don't use iTween in your game loop, prefer mobile friendly tweening libraries
-- optimize your physics triggers and rigidbodies if you have a lot ( using physics layers)
-- dont' use costly methods like gameobject find by string ( prefer tag based finding), and cache your references instead of searching everytime if you use the find action.
-- use a pool manager if you are instanciating destroying a lot of gameobject.
Also, the best way to go about mobile development is to test and profile on the deivec very regularly ( almost during and after each feature implementation) as you progress in your game development. This is critical!
Bye,
Jean