For her vest, I would recommend basing it off of a pattern for a button-down shirt with a collar. You would be able to crop the pattern to the correct length and simply leave off any sleeves included in the pattern. The buttons can be replaced with snaps – look for some with pearlized backs to them for the same effect as her vest. You will likely need a pair of eyelet/snap pliers in order to apply these, and may need to cut tiny holes in the p/leather for the prongs to go through before crimping.
You can use either a real leather or a faux leather for this project, depending on what you have access to and are comfortable working with. Be sure the material is soft and pliable enough to drape around your body, but not so thin that it doesn’t have the same effect as the render – it needs to plausibly look like a jacket material. Either way, be sure to stock up on some leather needles for your sewing machine to ensure the material can be punched through, and if possible, get a teflon/nonstick foot for your machine so you can do all the required topstitching without the material sticking to the foot. Note that with both of these materials, any holes or marks you make will not self heal with with regular fabrics, meaning that the holes will be permanent. Be sure to make a mockup or two and then mark your stitching lines on the actual material with something easy to remove (such as tailor’s chalk – test anything you use on a scrap first).
I would also recommend creating a bit of weathering on your material in order to get the worn-in look her jacket has. On real leather, this can be done with dye that is lightly dabbed on with a large-hole sponge or a balled-up rag. Be sure to not saturate the sponge very much! On pleather, you can use similar techniques but with paint. Use a brownish yellow base material and then use a reddish brown and a greyish brown in layers (once the previous layer dries) in order to get a similar effect to her vest. You can also add a bit of dye or paint dry brushed into the seams and along areas of wear once the vest is sewn to add a bit more depth.
For her tool pouch,I would look at how actual tool pouches are constructed. Here is a good example. They are generally a rectangle of leather with pockets sewn on the inside and then folded up at the bottom and sewn to create a larger bottom pocket. Experiment with some paper models or pieces of fabric to make sure you have the correct proportions and fully grasp the concept – I have a feeling that once you get it in your hands, it’ll be easier to understand how one goes together. You can then simply sew loops to the top that the belt would thread through.
I hope that helps! Good luck :]