Customs allowance when taking goods into the Czech Republic are 2L of wine, 1L of spirits, 200 cigarettes and up to 6000 CZK worth of gifts. When you are shopping at the airport, duty has to be paid on goods exceeding 30.000CZK in value. Duty on consumer goods is 19%. It is forbidden to export genuine antiques. If you have more then 350.000 CZK in any currency, you must declare it.
Are you smoker? Then visit duty free shops when leaving back home as cigarettes are there very cheap (£1 - 1 box).