I would actually disagree with a couple of the previous posters and say whatever you do, don’t buy a black suit. I think it tends to look very dated (unless it is a tuxedo/dinner jacket or tails). By the way, these are cut differently from a ‘suit’ as such.
Basically, people only weak black for weddings, funerals, very formal evening occasions (think James Bond in a casino), or if they are entertainers/musicians.
I suggest you go for very dark navy blue (this looks almost black), or very dark charcoal. Both of these would be fine for your wedding, and are also decent functional colours you can wear for other occasions.
Regarding fabric. . . I suggest you go for ‘natural fibers’ (i.e. 100% wool, cotton, linen, or whatever). Natural fibers crease more easily than fibers with a high percentage of polyester, but they look much nicer and are also cooler (important in Taiwan). You also have the comfort of knowing that your suit isn’t a fire risk.
Don’t worry too much about cashmere versus wool. Low grade cashmere (which is most of what is in the tailor shops here) is no better than good quality wool, so just go with your own feeling. Try touching the fabrics you see in the shop and you will get a feel for the difference. Cashmere is more for colder climates anyway.
Linen is good for tropical climates, although you tend to find linen in lighter colors. If you can find it, a rough linen/silk mix is very nice. Zegna used to do alot of suits in this kind of mix. It is nice to wear in a cool climate, and it stands out from the average ‘shiny suit’.
Hmm. . .Thats about all I can think of.