I've been trying to make a PCB but it's just so annoying having to sift through pages and pages of listings in order to find each individual tiny component without minimum order quantities of hundreds or more. The process of finding each component is so tedious that I gave up. (I was using EasyEDA hoping it would be easy to find components I could actually order -- nope)
DigiKey used to be a good place to get. Also design for parts you can get... In the old days you could also get samples from chip companies if you asked nicely. No idea if anyone still does that.
What kind of part? I use Octopart for a lot of things, like ICs (sometimes some variants are available in low quantities but others aren't and only in thousands).
For stuff like passives it's usually easier to use Digi-Key or Mouser and you can filter by MOQ so you only see things that are available individually.