Just remember that there's only three choices and they are a trade off
low iso needs a lot of light but is pretty. high iso can be in the dark but is ugly
small aperture (high f/stop) is a tiny hole so everything is in focus, but dark, so you need a lot of light. Large aperture (low f/stop) is a big hole, so you need less light, but only a thin slice is in focus.
fast shutter speed = less blur, but you need more light.
those three are the trade off.
https://photographylife.com/iso-shutter-speed-and-aperture-for-beginners
