Tooling wise you won't need much to get started as long as you steer clear of tooling/carving.
Even if you want to tool leather different providers sell basic carving kits for 40 to 50 bucks.
You can find YouTube videos on getting started and learn plenty there and here. Just dig around a bit and you can find some easy projects.
If your sister has an I pad, a slip for it would be simple enough. Just get a 4-5 ounce single shoulder. Then you would only need a basic square, razor knife, straight edge, stitch groover, an awl, sewing needles, some thread, and a cutting surface.
You may even have a few of those tools lying around.
Also, you would want to put a finish on it. There are lots of threads about that on here.
From one newbie to another, have fun. Otherwise, what's the point?