Zero. If a skill actually provides value, one of two things happens: it gets absorbed into Claude Code (or similar) within a week, or a company packages it up and charges real money for it. The "free skill that gives you an edge" window is essentially nonexistent. By the time you find it, everyone else has it too. You're better off learning to prompt well against raw API docs than chasing a library of pre-built skills that are either trivial to recreate or about to be made redundant.