The 3 beans will be use for 3 solutions :

1. short term,
2. medium term,
3. long term.

For the short term, I'm hungry. So, I'll to eat one first. What's the point of having magic if you die of hunger?
For the medium term, plant one bean, grow it and harvest more beans for more magic.
For the long term, save one just in case. You never know what people are willing to trade with you.