One of the most important detail in tailoring is choosing the most suitable fabric. A suit should not only fit your taste but also the weather. Check for its breathability because you would need to wear your suit for the whole day. Do not buy fabrics just because they are expensive because they might not match your lifestyle.
Cashmere is soft and expensive however soft may not be great for suit construction. No matter how much fusing you use, you must still remember that they are building a suit for you and not just a sweater.
Wools are your best bet however they tend to be too itchy or too stiff for some. But wools are still the perfect choice for a suit. Checking out the thread count is what you should decide on next. Thread counts should depend on the weather of the country you are living in or going to.