I have to say the majority of my Nationals clothes were found at thrift stores. I just don't have a lot of money to spend... particularly on clothes!!! Most of my money goes to board, vet bills, farrier bills, grain, supplements, shavings.... sigh...
Anyway you can find some VERY nice things at thrift stores, and for cheap! My purple blazer was $4.50, my burgundy prom-type dress was $3.00... you get the idea...
I've actually found myself getting sort of WAY too picky... last week I was looking at a couple blazers and found myself thinking "This one is $8.00... it's not half off like a lot of them... that is just WAY too much..." but then I remembered my $75 blazer just doesn't fit me any more (I bought it two years ago before I lost 35lbs) and so really, eight bucks isn't bad!!!
Anyway, eBay and thrift stores... that's MY big tip for you
Andrea