How to reduce time R takes for model building
Depends on the models you are trying to run. Your data isn't that big. For example using a support vector model from the kernlab package, you run into problems. Not every model is fast or has a fast implementation. 

Without more information on what you are doing it is difficult to say what causes the bottleneck. But if you just want a speed boost in running models, have a look at the xgboost package, the h2o package (GLM, GBM, rf, deeplearning), ranger for a faster implementation of a randomforest model.