Pokémon - GTS in a nutshell.

GTS? Reasonable?

Protip: All reasonable demands are usually in the first five slots. Reasonable demands are quickly traded so unreasonable demands are filtered to the back naturally as new pokemon are put up. If you want a reasonable trade continuously refresh the page to look at new offers before they are traded. A reasonable demand on a uncommon (migration/friend safari) but breedable pokemon that is commonly searched has a timeframe of about one minute before it is traded. If a pokemon is not breedable you will rarely find a reasonable demand because even if the pokemon is a piece of shit the lack of pokebank means scarcity (do not invest a good pokemon in a unown, the market is a bubble) which means a high price. Same goes more so for legendaries which are naturally limited.

tldr just keep refreshing