There are a lot of different custom options.
For example - cottons: Italian, Egyptian etc. it sounds gimmicky but it is not. Ask your tailor to explain thread count to you.
Wools: ask your tailor about the "hand" of the fabric - go with at least 120s. I usually get at least 140s or a wool/cashmere blend for suits, though you can go all the way up to 180s. On higher quality wools for example, you can wrinkle it, and then when you hang it up, the wrinkles disappear.
Also, climate is a consideration; I am in Florida in the US so everything is summer oriented.
Pricewise, a good custom suit with quality material should be about $2500 US, shirts should be about $200US.
You can get them cheaper but that wil come at the expense of quality.