Dip your toe in the water
Meaning: to try something slowly and carefully before you make a big commitment. If your first, small experience is successful, you might do something more in a bigger way. The expression comes from testing the temperature of water (in a bathtub, swimming pool, or pond) with your toe before you put your whole body in.
Example:
Before starting her own bakery business, she dipped her toe in the water by selling bread at a farmer’s market.
Judy Kobek, English Language Instruction 