However, if you are skateboarding on ramps, then you flat out need pads. Never skate a vert ramp without pads, unless you are seriously pro. And even then, it's a dumb idea. One mistake, one nail sticking up a little, and there goes your kneecap. Good times.
When it comes to helmets, You should wear a helmet. You might see skaters not wearing helmets, and worry that wearing one will make you look weak or stupid, but don't worry about it. It's common now for skateparks to require helmets, and it's just plain smart, especially when you first start out. You can read more details on Do I Need to Wear a Skateboard Helmet?