You need to cater to all stages of a butterfly's life - egg, caterpillar, butterfly. Caterpillars like food plants, while butterflies love nectar. Wattles can offer both. You also will need to avoid using any chemicals.
Melbourne Zoo has a great guide - http://www.zoo.org.au/sites/default/files/10-steps-butterfly-gardening-zoo-highlights_1.pdf
Flowers that typically have tubular or long flowers are pollinated by butterflies.