Butterflies don’t need anything fancy or expensive. Just a large, open, sun-filled area; some flowers, for adults; some food sources, for caterpillars; shelter; puddles; and rocks.
You might consider planting an herb garden if you enjoy herbs - many butterflies do too! Reserving a section of your yard for native flowering plants and for weeds like dandelion, nettle, and milkweed should also help guarantee a good variety of butterflies. It’s best to avoid using any pesticides at all.
Provide some shelter from wind, like a wall or hedges. Butterflies don’t drink from open water sources like a birdbath, so give them containers with damp sand. Butterflies like bright, dense blossoms like marigolds, verbena, asters, butterfly bush, zinnias, mums,etc.