Alter CSS for photo gallerys / create embed code

I am working on a series of portfolio galleries for my website redesign. I am wondering if the first need can be accomplished by altering the CSS. Please see attached file. 1) I like this gallery template: [login to view URL], but need to know if the CSS can be altered to add a space between the images similar to the space between rows, and still have the responsiveness work correctly. If this is possible, I would need to have you create that CSS alteration or new code and provide it to me, and show me where it goes so that I can complete other galleries on my own. I have attached all CSS files, I am guessing that you would alter the "Main CSS" file? 2) I know that this is probably simple, but need the embed code for this gallery. No PHP if at all possible please.... Thank you. Vic