Portfolio Theme Advice

Good mornin’
This is my 1st post, so please be kind! I’m trying to help a friend make a site to show his portfolio of paintings, however I’m quite new at WordPress and am struggling to find a theme that fits, after trying loads. It’s getting frustrating…

I simply want a page that will show jpegs of all of his images. When each of these are clicked then I want the image to show in a larger, centralised panel (called a lightbox…right?). A brief amount of text needs to be shown too (title, media, date) – either alongside the lightbox image or perhaps it could appear dynamically as hover-over text on the jpeg.

All the themes I’ve tried so far look ok with the portfolio, but when an image is clicked it just shows in the top left of a plain white page – not in a lightbox. Which doesn’t look very professional at all.

Ideally I’d want a free theme too, at least for now. Am I asking too much? Doesn’t feel like it should be too complicated.

Any advice massively appreciated. Thanks in advance.