Across online assessments, the transferable skills are usually numerical reasoning, logical reasoning, reading accuracy, prioritization, and staying composed under time pressure. You can also review the different formats in our consulting online assessment guides.
To improve, review your mistakes by type. Separate knowledge gaps from timing errors, careless errors, and questions where you misunderstood what was being asked. Then practice the weak category deliberately instead of repeatedly taking full tests.
Also practice under realistic time limits. Many candidates perform well untimed but lose accuracy once the clock becomes part of the task.