Data Transformation

I am trying to find the significance of a number of different variables on the level of a countries inflows from services as a percent of GDP. My variables include other data that is as a % of GDP, raw macroeconomic data, and data from the economic freedom index (a scale). When should variables be logged in this case? From what I have found, one should log data when interested in the multiplicative vs additive properties, leading me to believe all of my data should be logged? Can anybody help a regression analysis newbie?

Thanks in advance