What equipment do you need to play skateboarding?

When it comes to improvement, there is no substitute for practice. If you want to skate better, you gotta skate.

With that said, the efficiency of every move and motion in Skateboarding, or whatever your chosen sport is, can be improved upon by breaking it down into smaller sub-systems.

Almost every single sport out there (Chess and Warcraft don't count) require some combination of stabilization, balance, strength, endurance, explosive power, speed, quickness, and agility.

Improvement at the sub-system level will translate to better skateboarding by providing enhanced physical capacity, and it's resulting effect on the ability to complete a given move or motion.

Stabilization is the ability to control the body both statically and dynamically. Stabilization occurs throughout your whole body in many different ways. Stabilization of the core unit and at the ankle are especially important for skateboarding.

Balance is a state of equilibrium; a state in which the body has the ability to move in space in a controlled movement. You need it for obvious reasons. Balance obviously improves with practice and nothing can replace that. However, better balance in the gym will improve balance on your skateboard. Many companies offer products to enhance balance training. Who do you think does better on a skateboard? The athlete with better balance or the athlete with less?

It shouldn't be ignored, but...

Strength is extremely low on the skateboarding fitness list in terms of usefulness. Training for strength and training for power are completely different workouts. Power is one of the most important elements of skateboarding fitness.

Power is the ability to exert muscular strength quickly. When you see someone ollie really high, they are using power. Again, training for power is VERY different compared to training for strength. Significant improvement will only be realized by using proper training methods for power.

Speed and quickness is the ability to move the whole body quickly. I can't think of a single athlete in any sport that wouldn't benefit from being faster. Being faster gives you an edge over a slower opponent. Speed rules all. Speed can be improved with proper training. You can never be too fast.

Agility is the ability to start, stop, and move the body quickly in different directions. Definitely useful for a skateboarder in a variety of situations. The more agile athlete obviously has that advantage over his opponent.

Each of these elements should be targeted specifically to realize improvement and enhance your ability to perform.