I have read about general files that should be ignored in android studio project(What should be committed to the repository in the eclipse workspace?), but whenever i checkout to earlier versions on repo, i'm facing problems like difference in gradle version so i have to download gradle versions that i don't want to use in future and it is hard for me to download them.
so Which files on .idea directory should be committed to git repository? what about *.iml files?
Have a look here for an answer to your question. The IntelliJ documentation claims that you should share the following:
All the files under .idea directory in the project root except the workspace.xml and tasks.xml files which store user specific settings
All the .iml module files that can be located in different module directories (applies to IntelliJ IDEA)
I develop using IntelliJ, and I noticed that the .idea\libraries folder does in fact contain data relevant to the JAR files which are on my classpath. This information would be critical to anyone who wants to also run my project from their IDE on another computer.
