Please read my answer and bmike's comment before voting to close. Someone is going to come along and say I should just learn Mac shortcuts, but I must say I use Chromebooks, Windows, & Linux boxes and they all put the Ctrl/Cmd in the bottom left and right hand corner of the computer. I'm sorry but changing one operating system is way easier then changing the other three (especially considering Chromebook's native shortcuts can't be changed).
To alleviate the most common keyboard shortcuts, I have the left Ctrl mapped to the Cmd on my Apple computer. And have switched the right Cmd and Opt (Alt) on the right hand side. I then switched Cmd and Ctrl again in iTerm (a very well made application).
Now unfortunately Ctrl+Tab no longer works to switch between browser tabs. Well, tabs in any application actually.
I would like Cmd+Tab = Ctrl+Tab and Cmd+Tab+Shift = Ctrl+Tab+Shift.
I am on El Captain using Karabiner Elements and would prefer to stay away from Karabiner (the older version).