A good costume can be appreciated from across the room; a mind-blowing costume can be appreciated from less than six inches away.
Acting to me does not matter at all. Neither does having contacts, having certain props, or being lucky enough to have the facial structure of the actor who originally portrayed the character (for live-action replicas). Some of those things are personal preferences, some are dependent on budget, and the rest is dependent on the luck of your genetics, which isn't something you can control or has anything to do with your costume skill. It just means you have less work to do to make your costume stellar. Where the playing field is even is in terms of constructing the costume itself - everyone has the capacity to create and fit a costume to themselves, whether a novice or a master. If you want to go the extra yard, next level, whatever, you have to make sure your costume is impressive on close inspection and not just from a distance - proper fabric choices, proper fit, all the salient /accurate details, well-crafted. An amazing costume looks fabulous, and also makes YOU look fabulous.
Founder and Vice-President, Madison Area Costuming Society, a chapter of the International Costumer's Guild
Strange Land Costuming - www.strangelandcostumes.com