The bow ties you find in the store are typically make out of silk or some imitation silk poly. So it will come as no surprise that those are good options. Any type of fabric that you like the pattern or looks of can become a candidate for a bow tie. The only real limitation is that the bow tie will have to be turned inside out through a tube that is only 2cm across. With some thicker fabrics, this will be a difficult proposition.
Bow ties are more whimsical than normal ties, so having a fun pattern or loud colour is not as much of a problem as it would be with a regular tie.
Silk and silk imitation is slippery and tricky to work with. This can be compensated for with a fusible interfacing.
Depending on the fabric you chose for your bow tie, you will probably need interfacing. Interfacing comes in two main types; fusible and sew-in.
The fusible variety has some adhesive attached to one side that is activated with the heat of your iron. This attaches the interfacing to the fabric and the two can then be used as one. Fusible interfacing can be a great option if your fabric allows the heat required, and you use a quality interfacing. Some lesser quality interfacings can have the adhesive detach, and this shows as bubbles on the fabric surface later on in the life of your bow tie. Good quality interfacings and correctly following the guidelines for adhering the interfacing will not present these problems.
Sew-in interfacing is sew into place before the fabric pieces are used. You attach the interfacing to the fabric by sewing the two together inside the seam allowance. If you use a seam allowance of 6mm, you will sew the interfacing at 3mm. Anything may work as a sew-in interfacing, including an extra layer of the same fabric.
The key part of the interfacing is to give your bow tie the structure you like. You can have a bow tie that stands proud and crisp. Or one that droops a bit at the tips. This is all about your preference.
It is good to experiment with the interfacing on a scrap piece of your fabric, specially with the fusible kind. You want ot make sure you get the structure you like before commiting it to your pattern pieces.
Although the pattern calls for applying interfacing to all parts, if you have thick or stiff fabric, you may be able to only do one side, or no sides at all.