Best tools and ways for a diverse team

Hi all,

I've been coding for many years in many different languages.   I am comfortable with PHP and like what CI has to offer.  I am using it in a contract project.   

The one thing I have never been is a look and feel/art type person.  I can make the site look ok, but I don't have the artful eye to make it cool.  So my client has hired a designer who is familiar with CI and certainly knows CSS.

Our goal is to work together with him doing the look and feel, and me providing the CRUD and functionality behind the scenes.

We are physically separated and I tend to use different tools than he uses.  So I'm trying to figure out or come up with some ideas on a common set of tools we can both use that will simplify the process of allowing both of us to make changes, commit changes and push changes to a test webserver.

Our site is hosted on AWS Lightsail currently.  In order to send files to our instance we need to use SFTP which I am comfortable using but I'm not sure the UI guy is.

Back in the days of "FrontPage", yes, yes, I know  WYSISWYG web editors are the devil, the one thing they did have right was an almost one button push to your webserver.

I'm wondering what others are using and doing, in team situations with respect to tools, source control and pushing files to sites.  I'd like to find a good tool, willing to buy one, that will help both of us, UI and coder, to interact better and not waste time fiddling with various extra tools to get the job done.

I should mention we are both using Windoze 10 currently.

Any recommendations would be greatly appreciated!