Are you making a switch mode supply, or are you making a high freq transformer supply, such as a car stereo voltage booster?
Your original design problem probably was due to core saturation its one of the tricky parts of trannys, voltage and time need to be considered and the maximum flux density the core will take.
I have a little test jig which tells you the al value and gives an idea as to what flux density the core will take of a particular core, I re-use trannys from scrap tv's anything like that as inductors and transformers.
Dont expect to get a high efficiency supply straight away, theres a lot to consider in a switcher, however you can get a working supply with a little care.
A bulb in series with the incomming power to limit current has saved me a few fets and controller chips.