Contest descriptions are currently not reflecting the actual scoring requirements for the contest.
The text for 4 of the last 5 contests on server 21 have specified that diamonds are required, but the scoring screen shows gold or stamina instead.
In addition the contest that has just finished had individual progress reward requirements (I.e. 1 million for the top reward), but the ranking was done by guild rather by account. If this was intended there was no notification in the contest description.