Hi, how can I recreate in after effects this image, my goal is to make it pulse

You can simply duplicate the effect in the stack. AE basics. That said, sometimes things can't be done the simple way if you want them to look good and from years of experience faking light effects with feathered circles I can only tell that a "dumb" linear approach rarely ever works due to how the human eye perceives things. As soon as one of your circle begins to pulse, the feathering will seem to change thickness and colors appear to change when multiple instances are overlaid. You may simply not be able to avoid having to work with more layers and multiple effects to realyl make it look awesome...

Mylenium

Effect --> Generate --> Circle. Just stack a few of them and animate whatever parameters you need.

Mylenium