Don't get discouraged by low percentages early on. UWorld is a learning tool first and an assessment tool second.
Sometimes the explanation for why an answer is wrong contains the key to a future question. Is it Worth the Price? uworld usmle step 1 full
Waiting until your "dedicated" period to start UWorld is a mistake. The "full" bank is too large to finish in 6 weeks without burning out. Don't get discouraged by low percentages early on