BEST is subjective.
what is best for me, might not be best for you!
first--are you knitting toe up (one set of cast ons!)
or cuff down (another set of cast ons!)
how many cast ons do you know (1? 2? a dozen?
are you willing to learn a new cast on?
(and are you adventurous? or do you find it hard to learn out side a class(room) with out some feed back?
Long tail--or better a long tail variation..
especially Norwegian (aka german, or twist)
(or maine--which is the same (result) but different (method!)
Open and closed long tail is nice too, especially with 2 by 2 ribbing
Channel Island cast on is good too..
but even a knit cast on, with picots (basiclly, cast on some (3 to 5, then bind off some (2 or 3) then cast on some more..
(slow, but all those little bumps made when you bind off add stretch!)
If you really want a great cast on, a tubular cast on is fantastic for sock cuffs (there are at least 6 ways to do a tubular cast on..
and don't forget cross wise knit bands (icord is the simplest, and lace is more complicated. (there are hundreds that can be used!) but these are options!
for toe up?
Magic (Judy's magic)
you can google (or better search YOU TUBE) and find many tutorial (i have half a dozen or so!) for these and other cast ons..
the BEST cast on is the one you like best. (and only you can decide which one that is!)_