For your request smaller the board the better
Some general notes on boards.
Board size odd numbers always to stop a roadblock decision 1, 3,5,7. (yes in some situations you can have a single board member)
Try to keep board as small as practical, gets harder when adding new members due to VC or other investment
Expect to review board members yearly. (ensure board agreement documents this)
Expect to change your board members as the company grows
Try to avoid giving equity (in a small company you may have to - to get a name for market credibility - but over time that will change)
Most companies end up with 1-2 board seats from the company all others from investors or external board members that add value you don't have in the company
Finally, I would advice against an advisory board - esp. for a small company - far better to find some mentors to talk with and get feedback - plenty on this site after all