For lower end machines you'll want to start by switching to fullscreen mode, which gives you better performance right away. The trick with graphics settings is knowing what impacts fps the most - shadows and post-processing are usually the main culprits, so drop those first. When you're tweaking settings, watch out for v-sync, turn that off unless you're getting really bad screen tearing since it can tank your performance

Anti-aliasing is actually not too demanding if you stick with fxaa or taa, and it helps clean up those jagged edges without killing your frames. Maybe interesting - keeping textures at medium or even high doesn't hurt performance much unless you're really short on vram. The real performance killers are those fancy effects like motion blur, lens distortion, and all that eye candy stuff, so definitely disable those first

For the absolute best performance, you can dig into the config files to force even lower settings than the menu allows, but that's really only needed for integrated graphics. Speaking of which, if you're running on integrated graphics, getting smooth 1080p gameplay is totally doable - just make sure you've got shadows on low, post-processing disabled, and you're running in fullscreen. The light distance setting is another good one to turn down, especially if you're seeing stuttering in bigger areas