How efective is the visa k for bringing spouse to the united states ,how can I garenty that I could bring her and my kids with out any errors

It depends on your status, a K-1 visa is designed for a US citizen to bring in a fiancée or spouse. If you are not a citizen you would not be able to do this and have to look into other options.

If you are on a work permit, talk to your company about this, they should be able to arrange this.

K-3, K-4 is for the US citizen's spouse, kids(US citizen who marry their spouse outside of US). I think K-1, K-2 is faster since u come to the States earlier the only thing is that they give u a temp green card. K-3,K-4 they give u green card after u be in US for a while.