One fun challenge of gardening is finding two, three or four plants that combine well with each other. One suggestion to see "what works" is to visit other gardens, whether it be your local city, botanical, or fellow-gardener's, they typically have something that we may find useful.
Here's a first set of a few suggestions re. plant combinations. This is a classic combination of "layers" or horizontal bands of colour: Geranium 'Brookside' in the foreground, Iris sibirica 'Butter and Sugar' in the middle, and a Rodgersia is the background.
Here's an interesting combination of perennials and trees/shrubs: Geranium 'Rosemoor', Hosta 'Paul's Glory', a Cornus (my best guess) and a Blue Spruce. The purples/blues of the Geranium, Hosta and Spruce create some harmony, in contrast with the white flowers of the Dogwood.
Finally, a favourite shot of mine, of the flowers of Iris sibirica 'Caesar's Brother' leaning over after a rain, and lying on top of Hypericum 'Albury Purple'.
Here's to dirt under your nails.