Black and white/Beach party

Hi. I am turning 16 a week before christmas, but I don't really have a theme and don't know how to develop my ideas.

I'm on a really tight budget, so it can't be expensive.

I was thinking about going down to the beach and blowing up balloons etc and somehow acquiring a stereo or something to play music on the beach.

But I don't know what else to do there.
But then I thought I really want a theme, like black and white (or something like that) in a room, but it's too expensive to rent out a hall and I'm not sure how it would look in my house.

And again I don't know what to do to entertain the guests. All I know is what dress I'm wearing (my friend made it for me) and that I want to take pictures of all the guests but somewhat fancy with a backdrop or something, like what you get at a school dance.

So please help, I can't decide between my ideas and I don't know how to go about them inexpensively.

(BTW there will only be around 10 guests)