I first found the DR when researching the best beaches in the Caribbean.
I was looking for Robinson Crusoe quality beaches, and I found literally miles of them there.
My suggestion is: fly into the North shore [POP], Puerto Plata,...and then explore...working towards the more tropical eastern shores, ending up at the Samana peninsula.
Beachfront towns that are worthy of note are:
Sosua: A lively European flavored town with hotels priced from only $15!
Don't believe it?
Rockys Plus,,,That price includes free airport pick up!
Look for more great, budget beach locations to follow!