Most of the FX I make use like three different textures. : A ring, a circle and a full square :D. It's all about animating them and using sub emitters. A good FX uses usually 4 to 6 sub-effects to add some punch !
No shaders required most of the time, besides one I had to make to blend alpha and emissive on particles over time. It's not possible as is on the default particle system, maybe on the VFX graph idk