You are not expected to buy designer fabric, often it is very expensive, and I only buy it if I drop on it in a sale, so either go with a design or look that you feel sums up the country you are representing right now. I am not going to specify what type of fabric you get but I would recommend steering clear of cheap and nasty polyester types, if in doubt go with cotton.
As for the size of the fabric, I think most countries use metric these days, just go with whatever your country uses, there is very little difference at the end of the day. You will need 2yds /2m of fabric, one of each type, a traditional and a contemporary. Fabric is usually sold off the bolt and is usually 44"/110cm wide (knits and upholstery weight fabric is often different). So you should have 2 pieces like this....
So, simple cut into 4 quarters like the diagram above, you send three to your swap partners and keep one for yourself.
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