It is very common in speech, at least in the US. Note that it's OK, not okey. If someone falls down, you jump to them and say "You OK?" or if someone looks distressed you can say "Everything OK?" Those are perfectly fine, but don't use it in school and business.

Yes, it's common... but it's much better to include "is" at the beginning.

希望在累成人干之前学会分辨哪些是“不重要的词汇”.T_T

当你说多了，说习惯了，你有时也会省去一些不重要的词汇的。