I'm going to add a couple of additional comments since you indicate you are just starting out:
- Hopefully you have a legal contract that the law office signed. This should provide details of your role as a legal assistant, responsibilities, etc.
- In conjunction with bullet number 1, your facts don't indicate what the "errands" consist of. Are these errands part of the role of a legal assistant or are they errands that are personal in nature that the attorney doesn't have time to handle? This is key, as if it is the later, those won't be deductible as they are not ordinary and necessary expenses to perform the role of a legal assistant. While you may believe they are necessary to stay "employed" they aren't necessary for the role of legal assistant.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
