Costuming fantasy can be a lot of fun, and "Alice in Wonderland" is no exception. The illustrations in the many editions of the classic are a great place to start.
A little color goes a long way. Choose a pallet, and create all of your characters with similar color values, such as pastels or jewel tones. Creating each character with a monochromatic scheme--varying shades of the same color-- works well.
Choose a style and stick with it. If the Mad Hatter is dressed to the Victorian nines, a March Hare with ghetto attitude will be out of place. Whatever your design aesthetic, consistency is key.
Creating alternate universes can be expensive and time consuming. Use a 3D modeling program to map out your staging. The better your plan, the faster and cheaper it gets done.
Use what you can from the real world. A bright coat of paint can turn ordinary wood tables and chairs into fantastic furniture fit for Wonderland.
Giant mushrooms, storybook cottages and castle courts can all benefit from a little foam. Wire forms upholstered in foam can make mushrooms, and sculpted styrofoam thrones and castle walls are fairly quick and inexpensive to make, not to mention easy to move.
Build the main element in each scene, and suggest the rest with paint. Latex paint is cheap and can be applied to almost anything.
Props set a superior production apart. Staging "Alice in Wonderland" is the perfect opportunity to flex your prop-making muscles.
Exaggerate everything, from double-sized croquet mallets to giant teacups. Buy teacup-style flower pots at a garden center, and use 4-inch PVC pipe and fittings to fashion croquet mallets.
Spray paint is your friend. It comes in a wide variety of colors and will stick to almost anything (except styrofoam; it will eat styrofoam). Test a small piece of the material you wish to paint to check for unexpected issues. Allow it to dry thoroughly before assuming everything is okay.