|Most people use something like 1/4 to 1/3 of the recommended amount. Most detergents companies size their lids to accommodate at least the largest possible recommended amount, but you really only need less than the minimum amount (the more detergent you use each load, the more you buy, and how many people don't just put in a lid full instead of reading the container?). This won't look like much, but it's plenty, and really you could wash all of your clothes just fine with way less than they recommend. Perhaps someone who uses Tide Free can comment on how much they use, because I think Tide lids give you something like three hash marks, but if you don't get that specific comment, I'd figure 1/4-1/3 of the way to the first (lowest) line.
Typically, new diapers should be washed 3-4 times to remove the oils. They don't necessarily need to be dried in between those washes, though.