Lime juice must be from actual limes, not RealLime® or Roze’s® Lime juice. Squeeze some damn limes! You can freeze lime juice for later use and it works fine.
I base everything on however much juice comes out of a lime, by weight. It’s easy to use a scale for this (but somewhat nerdy)
combine them all in a shaker with a bunch of ice, and shake the heck out of it. This chills the mix and thins it with some water (this is important)