The surname 贾 has two readings: jiǎ (as a surname; e.g. 贾宝玉 from Dream of the Red Chamber) and gǔ (the verb 'to do business'). For names always use jiǎ.
culture
贾 is most famously the surname of the Jia family in 《红楼梦》 (Dream of the Red Chamber). 宁 is a calm, fortune-bearing name character meaning 'peaceful/tranquil', popular in given names for both genders.
