Booking a vacation to Punta Cana, looking for one cheap what do I need to make it perfect?

My boyfriend and I will be taking our first vacation next spring for a week. We've decided to go to Punta Cana- we want the best vacation for the best money. It's our first real solo vacation and am just wondering what tips anyone can give me.. what needs to be done i.e passport, vaccines... etc! Any help will be great thanks :)