All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
There is no Zakat on the land that has been bought for the purpose of building a house. Had it been bought for the purpose of business, Zakat would have been obligatory on it if it reaches the minimum amount liable for Zakat, and a whole lunar year elapses on it. In this case you would pay 2.5% Zakat of its price.
As regards the Zakat on gold, it should be calculated from the whole quantity and not after deducting the minimum amount liable for Zakat.
So if you possess, for instance, 300 grams of gold, you should pay the Zakat on the whole 300 grams, which is 2.5%, i.e. 7.5 grams.
For more benefit, please refer to Fatwa 81977 for the ruling on the calculation of the Zakat on gold, and Fataawa 88895 and 86363 for the ruling on the calculation of the Zakat on jewellery.
Allaah Knows best.