Designing a poster for an event is always done in different ways. Differs in complexity, style, the possibility of improvisation in design. If a set of classic tricks that have been used for years and barely change.
For example, the design of a sports poster for a football match, boxing match, any championship, etc. always has some common details. Usually this is a combination of photos of participants, some additional elements that reflect the general meaning, description of the event, a list of people / countries / clubs that participate, dates, venues, sponsors, etc.