During his 28 years with the World Bank, Gaiv worked on private sector development, public enterprise reform/privatization and financial sector development/financial inclusion. He also worked on country programs in Sub-Saharan Africa and MENA regions and managed the policy aspects of two IDA replenishments. He served in various positions including as: Director, Financial and Private Sector Development in Sub-Saharan Africa; Director, Global Practice on Financial Inclusion and Infrastructure; Deputy Director of 2005 World Development Report on Investment Climate; Manager, IDA Resource Mobilization; and Country Program Coordinator.

Since leaving the World Bank in 2015, he has continued to support, assess and evaluate programs in private and financial sector development and concessional finance/aid architecture. His consulting assignments have assisted regional development banks (African Development Bank, Asian Development Bank and Islamic Development Bank), the European Commission and the World Bank.