Best ways to apply fancy effects on a plane?

Hello, I am building a painting game where I have some 2D sprites and I can change their color. Basically a raycast checks the collider and changes the color of the parent collider.

I wanted to add some fancy effects, like sparkling colors, alpha maps, gradients, etc but I am facing some difficulties.

What would be the best method to apply those fancy effects on a sprite? What I tried so far:

• Apply gradients: I can't apply gradients on sprites, but only on textures.

• Apply sparkling effect: Apply a texture on the sprite and animate it? Using a shader? As last resort I'd use the particle system with some sparkles..

• Apply shadows, transparency maps, etc.: Shaders? Apply some sort of texture on top of the sprites?