Like Peter, I pretty much always use measuring spoons for yeast, sugar, and salt. I used to measure oil by volume, too, but I've come to realize that oil is almost always something I can measure pretty accurately by weight, even if I use my 32 oz mechanical scale. However, I now also have a cheap digital scale that measures in either ounces or grams, which means I always measure oil/fat by weight nowadays (in grams). (I've also been trying to convert my brain to thinking in metric measurements, but that's not easy.) My digital scale is only accurate to within 2 grams, but I'd imagine that's just as accurate as measuring with a spoon. I'd like to get a scale that's accurate to within at least 1 gram. If I do, I'll probably end up measuring all my ingredients in grams.
Just don't geek out about it. As you gain more experience, your understanding of all this stuff will come together, just from the repetition and stuff like that.