If you want to world build, read a lot of history. Fiction is great too, but taking too much from fiction can lead to cliches if you are not careful. History is an incredible tool for getting ideas because it is filled with all these little instances and practices that are hard to make up. Having a deep enough understanding of world cultures, past and present, is also good because it allows you to deconstruct them and take the bits you like in order to make your own culture. If you invent a culture and it is the exact copy of a single real world equivilant, it won't be nearly as interesting as one you construct from so many parts that it becomes its own thing.