D/D/D deck is a combo deck with huge potencial (and also my favorite deck of all time, as well). In 1 turn, you can put up 2-3 negates, and powerful monsters as well. However, if you brick, it won't end well, and this deck can easily brick. So, in my deck, i put in a lot of draw cards, in order to draw the pieces you need in the combo.
If you don't know how to play, i recommend watching youtube video about how to combo properly, like
this and
this!. Good luck dueling, and have fun!