Here are some quick trips that I have tried to speed up Android Studio on my Windows 8.1 Laptop. I hope you have a laptop with 4GB RAM because that is recommended.
1) Un-Comment (if there are commented) or if they are missing then add these 2 lines to the project gradle.properties file (See image below)
org.gradle.parallel=trueorg.gradle.configureondemand=false
3) In android studio, you can enable offline work to make android studio run faster. To enable offline in android studio, just follow following step. In Android Studio, go to file >> setting and click Compiler from side menu and then type --offline in the command-line options box and hit OK button like this: