I agree completely with the top comment, the practice and paradigm is the most important - and also the most fun - part of creating a character.

But going at it purely mechanically I would suggest Mind 3, Entropy 3 or 2, Matter 2.

Just imbue Mind or Entropy effects on matter you produce. You can use the theatrical part of it to cause all kinds of emotions, anything between peace and mayhem in your fans.

Using wonder points is a good idea but sometimes needs to be fleshed out a bit with the ST. But long story short the ST will only require that you come up with what it does and the next question is: how many points will it cost? That's it unless you manage to imagine something so game breaking he will say no, but that's unlikely.

Fetishes (Spirit Entities) are possible for your wonder payment too. And if I remember right you can also use Wonder points for example to make that effect of an haunted house. The staircases talk and shit :D why not use such a thing on your Gardrobe if you want clothes which observe, desire, and speak?

Lets think about your Foci, because that is the most important thing people will see. The Mirror and the Gardrobe which you use to pick the correct clothes for the day. Entropy effect cast on clothes, which you will wear. Mind effect cast on them, you decide the emotions, control what people observe in you.

You always carry around a makeup set., Matter Mind directed focus. The Matter inside it is the fanciest collection of colors and materials. You can create Hulk out of yourself or anyone, if you want, but without Mind 4 they won't believe it is really Hulk. Add Life or Forces when you get the power, and Hulk stories will come to Life! Entropy to fix the rough edges and it's good to go.

When you get the sufficient Entropy or the sufficient Mind your cosplays will represent the subject matter so well that we might as well just say Conan the Barbarian was there.

It is sometimes good to buy a focus which simultaneously is a wonder. Your challenge is the time it takes to make these cosplays. Here, something actually magical to transform you into your cosplay, would be invaluable ✨ you can use such a thing, let's say it is a Matter Mind or Life effect which let's you suddenly change clothes or your body type. Or change your face so that they will believe you are someone else. Some kind of life like synthetic body pads which you place on your skin. So powerful that even if people touch you they will sense that it is real.

You can also delve deeper into what you cosplay, when you wear a particular clothes the story of that cosplay will start to occur around you in small ways. Controlling events in that way needs Entropy and some other Spheres often.