The original poster probably still isn't trying, but for those who might come along with interest in this subject, the answer is that if you try to use real soap soap as bubble bath, you have to put enough soap in the water to completely "soften" (i.e. use up all the calcium in) it, which can be an enormous amount for a decent amount of bath water that's average "hard', and additional soap to make suds. An account from 1943 -- http://news.google.com/newspapers?nid=1499&dat=19430824&id=4CwaAAAAIBAJ&sjid=_SQEAAAAIBAJ&pg=1818,3432373 -- tells how much soap that was for a pool for a movie effect, and how until that point was reached, all it made was scum. And at that, soap makes a relatively irritating bubble bath compared to other materials for the amount needed to make a foam on bath water.
Look at the ingredients on a package of bubble bath. Yeah, ingredients like those, not soap, are what you need. I did it myself -- http://users.bestweb.net/~robgood/lather.html -- using ingredients called sulfosuccinate esters and glycine betaines. They're like soap, but milder, and don't react with water "hardness" to make a scum.