我會係10月尾去捷克旅行,大約7日!有問題想問問大家?

The weather should be quite comfortable, evening may be a little cooler.
So just a thin jacket should be enough.

I usually recommend exchange some local currency (Czech koruna) before
the trip, enough for say 2 day's use. And then you can get additional cash
at local ATM machines.

Phone card I donno, I didn't carry a phone last time. I don't even know
what system they use, is it GSM?

7 days, you probably should go out of prague. I'd say prague can take
you between 3-4 days, and then you can go out to other citiies. If you don't
yet have in your mind which city/cities you want to go, try reference -
http://members.tripod.com/~zlimpkk/Topography/mesta1.html

I don't have "things to buy" list for you, but I do highly recommend Prague,
I went 3 yrs ago, I love the city. Just soak in the culture and atmospher of
the Bohemian world!

Vitus Cathedral at Prague Castle is wonderful, especially if you can do some
study about the history of prague and prague castle before the trip, you see
much more by doing your homework first.

Have a great trip!

I went to there two years ago.
The weather at that time should be quite good and suitable to travel.
Currency is not a problem. You can either change it in advance or change there. You can change for Czech Krone in the airport or railway station.
I don't know where to buy the phone card but if you want to dial international call, just use visa card will do.
You may buy some sovenirs like small figure with traditional costume, some small landmark architecural buildings, etc.
Besides Prague, you should also go to another city Karlovy Vary, which is a city famous of spring. At there you can buy some special shape of cups for drinking the spring water. Also, you can enjoy the hot spring there. So bring with your swim suit.