The UN has several sources of datasets relating to government expenditures and trade that are free to use for commercial and non-commercial usage. Generally, the terms require attribution.
Note, not all UN datasets are free to use.
UN Data - data.un.org
All data and metadata provided on UNdata’s website are available free of charge and may be copied freely, duplicated and further distributed provided that UNdata is cited as the reference.
World Bank - data.worldbank.org/
You are free to copy, distribute, adapt, display or include the data in other products for commercial and noncommercial purposes at no cost subject to certain limitations summarized below.
You must include attribution for the data you use in the manner indicated in the metadata included with the data.