How do you make new particle systems?

I honestly have barely scratched the surface of what is possible with particle systems in Unreal. Before I delve into it though, I felt it important to know something first. Am I limited to putting together PS using only what is in Unreal, or is it possible to create new graphic effects outside of Unreal in say Blender or another external program? Or is everything I need to make anything conceivable already in the engine?

Just want to know all my options before going ahead.

Also, do materials play a large part in changing how particles look? I had no idea until just 10 minutes ago that materials have anything to even do with particles.

You can create textures in any photo-editing/drawing software you can think of.
you can create intricate materials, apply them on meshes and emit them from particle systems.