My grandfather in his knickerbocker/plus-four outfit from the 1930s. Such trousers can also be worn with all manner of knits (Fair Isles are a classic with such breeches and bold colors and patterns lend themselves rather well to this look), British-cut sports coats; that is to say hacking coats and Norfolk jackets and most types of felt or woolen hats dependent upon taste. These breeches are really appropriately worn with ankle boots which should either resemble Tricker's ankle boots, or Balmoral boots though, they may also be worn with gaiters and low-shoes such as brogues that is unless one is just wearing the suit for carousing about the town as my grandfather is doing here. The hosiery worn with such trousers should be of a reasonable weight which will complement the weight of the material used to craft the breeches.
A note of interest; bold even gaudy checks and plaids were rather "in it" back in the twenties and thirties and slim-cut breeches which were given new life and cultural validity by such firms as Jaeger, were still popular and prevalent throughout the twenties which was after all, the age of "Gatsby". The baggier models came in a bit later. Tweed caps of various types were popular with breeches as were cardigans and pull overs of various types. Just remember, bold and since this is Gatsby-esque; SOFT!
Me personally, I always prefer my breeches to be regular button cuffed breeches in a woolen tweed, I do not go in for "plus-fours" preferring the old style of breeches which are still worn for hunting and shooting and which are available from such gentleman's outfitters as Cordings of Piccadilly et all. Though, a bold check it always nice!