Study up on fabrics.
It's time to learn about Super 120s, cashmere flannels, and Harris Tweeds. Though the sheer number of different fabric types can be overwhelming, it's easy enough to manage if you follow this simple advice: Your first bespoke suit needs to be good for three seasons. It should be dark, and you can't go wrong with blue or gray. Does that sound boring? It shouldn't. Have a look at the suits Sean Connery wore as James Bond. They're dark, conservative killers.
The weight of fabric is also important. There are lightweight flannels that will not make you feel the heat. But you should tell your tailor if you sweat easily. He can guide you to appropriate fabrics.
There are more blues and grays to choose from than you can imagine. Don't look at them in isolation: Consider the color of your skin and the color of the shirts you prefer. Your tailor should have a good idea of what has worked for men like you and will understand the restraint needed to avoid the bolder patterns better suited to men with walk-in closets. Here are the fabrics you should seek out.
Worsted Wool: Versatile fabric made from worsted yarn. A standard for solid-colored suits.
Super 120s: A luxurious lightweight wool that is ideal for a three-season suit. Super 100s and Super 150s are also available. All are good.
Mohair: A silky fabric made from the hair of the Angora goat. It has a bit more texture than other wools and is an interesting counterpoint to an oxford or broadcloth shirt.
Flannel: You know flannel. Tailors usually have a wide selection of grays and weights. It's possible to get a suit that breaths easily and can be comfortable come spring.