I just did a regression based on the gravity model where I try to identify the most important factors that determine the trade flows. In total I have 18 variables and 363 observations. In fact I would do several regressions not including all variables at once. Although I included them all just to have a look and I got an R-squared of 0,9162 (using robust standard errors). Due to poor data availability for certain variables I only have 102 observations by including all variables. The problem is that only 9 coefficients are significant at the 10% level. Can I now assume that only those variables have a significant impact on trade flows? Can I assume that the regression is good as R-squared is quite high? Or can I do some tests whether those results are reliable (so that I can use them in my research paper)?
I am doing this for the first time and I am a little bit confused.