In the state of Wisconsin how much money can a parent gift a child without being taxed on it?

WI does not have a gift tax, so no problem there. As for the feds - any individual can gift up to $12,000 to another individual in a year without tax consequence. A couple filing as Maried Filing Jointly can together gift up to $24K. If you gift more than that, there are implications regarding the lifetime exemption of $1M for gift and estate taxes. See Pub 950 for details:

Publication 950 (8/2007), Introduction to Estate and Gift Taxes