Buying within in the EU is fine - you'll obviously get no taxes
Buying outside the EU then you may well get charged VAT and import duties on whatever amount the shipper has put as declared value (unless the shipper has said it's returned goods I think). It tends to amount to about 30% extra which is a hefty amount

ush:
I have bought jeans and clothing from Revolve Clothing in US many times and just occasionally - say 1 in 5 times - the import office has let my items through with no taxes....doesn't happen that often though and I can only assume it's an oversight on their part

Whatever, jeans are so ridiculously priced over here it still works out a fair bit cheaper to buy them from US
Marking as a "Gift" only helps if the item is worth less the about £35.