How do I prevent a tacky wedding?

With chemo bankrupting me a bit ago, I only us want to spend about $4000 on my wedding. (It's my fiance and I financing it, and we are in our 30's) I have always dreamed of eloping- to me it seems so much more romantic, and I have never wanted to walk down the aisle in a big white frock of a gown. I would feel like I was on stage in a play. However, now that the time has come, I do want to have family and close friends there. I would consider myself a hippie born many years too late as I would prefer to get married outdoors in a breezy dress. Is there anyway to pull off something casual like this without looking tacky? There's a fine line between cool and tacky or cheap. Any ideas, or am I doomed?