Editing photo question, complete beginer

it's kind of has  a nod towards Low Poly style,

with a blood splatter type brush sploshed on.

So you might want to look at low poly videos or tutorials eg on youtube

Maybe they did all manually  or it could even be based using an action in Photoshop

something a little  similar to this one

https://graphicriver.net/item/geometry-and-low-poly-art-photoshop-action/18096567?ref=rojdark&clickthrough_id=1405060763…

You'd do it largely the same way you would on paper. Imagine you have the photo under a sheet of trace; these are your Illustrator layers. Then, by choosing lines to accentuate and drawing over them, you slowly build up a composition.

Where your job gets easier is when it comes to filling areas. You might make a live paint group from your composition, set up a palette of swatches with patterns you're going to use from light to dark, then just click where you want to fill, paying close attention to the dark and light areas in the original image and again accentuating areas for artistic effect.