The choice of propeller will depend on how you want to use the boat, and the weight it would carry for the majority of the time, i.e. the number of people. Basically the lower the pitch the greater the acceleration or the more weight it can carry and still be able to plane. The higher the pitch the faster it will go but it will take longer to get on the plane in the first place. I would either recommend an aluminium prop or a stainless steel one. The s/s is more expensive but should give better performance. I would steer away from composite propellers as they generally give less performance and are more expensive to repair in the long run if you damage it as a single blade replacement is about £20-£30+VAT whereas you can have an aluminium prop repaired (all blades) for £31.50+VAT. As a beginner I would recommend that it would probably be best for you to start with an aluminium prop and maybe upgrade to a s/s one later. Which ever you chose keep the prop in good condition as any damage to it will affect performance.
Hope the purchase goes well and welcome to ribnet
propeller repairs & sales