Optimizing Linear Regression Machine Learning

Hi All or @SupportOfficer1 @SupportOfficer2 ,

I made a linear regression modelling to forecast revenue and used around 25 variables as below flow but still not getting a good result. can someone suggest any optimization method to improved the result ? I already used features selections and cross validation.

the variable contain data like number of samples, number of populations, wealth index, actual revenue as references