Needles are available in a great many sizes ~ and with many variations on the shape and materials used to make them.
Teachers concerned about Health and Safety requirements may be glad to know that slightly less sharp ~ blunt ~ needles are available. I call them bookcrafter's ~ or bookbinder's ~ needles. (Although other needles have that name also ~ time for an official ruling!) Blunt neeedles are not suitable for hole-making ~ an awl is required for that. Most book-makers use one ~ so no problem there. Tapestry needles are useful ~ their eyes are very large.
Even less 'pointy' are plastic needles ~ often sold as children's needles. These also require a large hole. Binding with wool is a suitable gap-filler.
Most of the above are available in different lengths ~ and widths. They are often coded ~ No12 ~ #14 ~ and this can be confusing if the manufacturer's decode is not available.
'Which needle to use?' is a choice for each individual ~ depending on experience and talent. The choice of thread will need to be considered.
In general ~ for bookbinding ~ holes should be made with a very sharp awl. Once the hole is made a blunt needle will steer itself more easily through the hole. A sharp needle ~ if not controlled with great precision ~ will wander off course and spike the paper surrounding the hole ~ or it will catch any other thread that may already be snuggled in the hole. All but the thinnest needles make larger holes ~ that might not be acceptable to some people.
Threads are available in a great many sizes ~ and with variations on the materials and methods of making them. Traditionally the bookbinder uses linen thread ~ it is strong, long lasting, and readily available in a variety of widths and colours. Linen thread is made from natural fibres. Modern polyester or nylon threads have different properties ~ but are often chosen in preference to linen. Cotton thread is generally regarded as being too weak to withstand the wear and tear of holding the pages of a book together reliably.