Even one card can be an insightful spread, and will help you form connections with and gain insight into your deck.
There are different ways to approach it--
Draw one card, prop it up on your desk, and leave it there untill you have written a page about it.
Draw one card each day, to answer the question, what is the theme of this day? Sometimes the theme will be manifested in things that actually happen, other times it gives you a different viewpoint on things that are only tangentally related, and some days it is just a focal point for thought or meditation. Write about the card and it's bearing on your day in your journal.
I always have the one card study going on, sometimes for weeks at a time if I can't connect with the card right away. I go through phases with the daily card. Sometimes I'm too busy living life to even think about it, and other times it's really important to me.