Question: how many avios points do you need to book a flight?
Answer: As this ba.com page explains, flight redemptions start at just 4,000 Avios. This will get you a one-way ticket in Economy to Amsterdam, Paris etc on an off-peak date. Long-haul Economy redemptions start at 13,000 Avios, which will get you a one-way seat in Economy on BA to the Middle East or India.