For getting acquainted with the language and for travelling we recommend Colloquial Breton.
There you find the basics including grammar and an explanation of pronunciation in order to understand and be understood.
If you want more vocabulary without trying to become a professional, then we recommend the Hippocrene Dictionary and Phrasebook Breton-English / English-Breton.
This dictionary contains two parts for both translation directions, although the vocabulary is not very comprehensive.
