Blood System

To stay in good shape you should drink once every week AT LEAST
If you go too long without drinking [Or not drink enough] you will start to decay while your still alive, If this goes on for too long [A "few" years] you will Die for Good
Note: Pure-Bloods don't die from the lack of Blood they just keep decaying... Forever

Vampires Need Blood

Vampires require Blood to stay alive and functioning
If they dont feed on blood, There will be Consequences

Vampires Blood High

Vampires who just fed are stronger for about 1 Minute [It's up to the DM to decide how big the buff is] [Must be fresh Blood]
Side Note: Vampires who just fed are going to have a harder time controling their Bloodlust

Stages

Sated
Thirsty
Parched
Blood Starved [At this point, Your Vampirism is so obvious that onlookers will be able to tell that your a Vampire]