Clichs and idioms should generally be avoided in favor of direct, literal expressions. Lion's share is often misunderstood; instead use a term such as all, most, two-thirds, or whatever matches the context. The tip of the iceberg should be reserved for discussions of icebergs. If something is seen as wasteful excess, do not call it gilding the lily or white elephant; instead, describe the wasteful thing in terms of the actions or events that led to the excess. Instead of writing that someone took the plunge, state their action matter-of-factly.