I'm using FileMaker 12 but want to get a version that syncs via free iCloud or Dropbox type service (you can only do it manually in FM12). What is the earliest version that does this? Its for personal use and I don't have much money so I just want to get a cheap older version of FM but want it to sync across all my devices.

None do it natively. It's not really that kind of app. While, technically, you can sync the file using Dropbox, there is a large and very unforgiving list of issues with doing it. Can it be done? Yes. Do you risk corrupting the data while doing it? Yes.

You have to make sure the live file is not being touched. Before you open it on any other device you have to make sure it finished syncing. And if the file ever crashes, you need to revert back to a back up that hasn't crashed.