What weight on Dumbbells should i start with?

I'm nearly 16 and i've decided to go on a health kick, get myself in better shape to please myself.So i'm starting to get things together that i need/will use at home (No gym membership, i cannot drive(too far to walk), and my parents work) I want to build my muscles up as-well .

So my question after all that rambling:

What weight should i start out on dumbbells?

2014-06-26T20:48:56Z

@Joseph, Thanks. Should i start with something that's easy for me and build up from there or start with something that strains me a little more? *Stupidity at its finest*

?2014-06-26T20:27:41Z

I started with twenty fives. But thats only because that was all we had, if you get a chance, go to a sporting goods store with a friend or something and test out their dumbells, or get one of those sets where you can adjust the weight.