Photo Grid with lightbox

I’m working on creating a wedding photo site and would like one very simple thing-a grid portfolio where if you click on an image it pulls up some sort of lightbox and you can scroll through the series. You should be able to click any photo in the grid and arrive at that image in the lightbox and be able to scroll from there. I’m having a really hard time to figure this out and it doesn’t seem very difficult. I just purchased a theme (purity) from themeforest, and it’s galleries definitely do not have this. Is there an easy way to do this? I really don’t want to pay for another theme or plugin but will consider it.