You get Moxie by getting a Magikarp with Rattled, its Dream World ability.
That site will let you play Flash games to get DW Pokemon, or you can find someone willing to trade you one.
And Moxie isn't better or worse. It helps facilitate sweeps, but Intimidate is better if you plan on using a bulkier set, or plan on switching more often. --- "Murder of the living is tragic, but murder of the idea is unforgivable." - Janus, speaker of the synod