The correct needle is dependent on the thread you are using. I often use 'Sharps' the size I determine by the weight thread I am using. If I am using metallic threads I use a needle specific for metallics. Some times I use a topstitch needle (usually when working on heavier fabrics like denim, or when using a heavy thread. Superior Threads is a good place to visit. They have charts you can print off explaining the different threads and what needles to use with them it is a very good resource. I buy needles from them sometimes too. I often use Schmetz needles. They've have worked OK for me for 50 years