I don't want to frontload the player with a bunch of information at the very beginning of the game. I think it would be desirable to have most of the buttons hidden at game start. They only become visible when an event has taken place. For example; the map button doesn't need to be shown until the player has a new location to visit, the health meter is hidden until there is change in health, the inventory button is shown when the player has picked something up... the list goes on. The new buttons should be accompanied with a short descriptive text, something like a tool tip. Maybe a flash or animation when they first appear to alert the player of the new functionality.
For your amusement I have put together a picture showing the different HUDs I've tried.
The bottom most picture is the current iteration. The back frame in gold will expand as new buttons become visible. The health meter is outside the view, floating in the upper left corner. I've intentionally made the buttons rather big in the current version. They should be easy to click/select since there aren't that many buttons.
Thanks for reading! =)