The sport of soccer has very few basic equipment needs. In fact, any player can work out with nothing more than soccer ball. As a player grows in skill, and joins a team, the equipment needs grow.
Step 1 - Soccer ball
Soccer balls come in three different sizes. Size 3 is the smallest, and is used by children under the age of eight. Size 4 is the next size, used by children between the ages of 8 and 12. The largest ball is size 5, the standard size used for those 13 years and up, including adults.
Step 2 - Cleats and shin guards
Soccer cleats have a specific formation of the "spikes" on the bottom. (A baseball cleat has a spike at the toe. This spike is not found in soccer cleats.) Once a player is competing at a higher level, only soccer cleats are allowed. Shin guards come in many varieties. For the younger set, they involve the actual piece to protect the shin, as well as some type of padding around the ankles. These are held in place by Velcro or elastic straps around the back of the leg, and a stirrup going under the foot. For older, more experienced players, moldable shin guards are used.
Step 3 - Goalkeepers
Soccer equipment for goalkeepers is different than that for field players. The most important thing a goalkeeper needs is a good pair of gloves. There is a wide selection in a variety of price ranges. Some keepers prefer gloves with finger stays - supports to keep fingers from hyper-extending when fielding a hard shot. Other keepers feel the stays make it more difficult to punch a ball. The keeper also wears a special jersey, usually long sleeved, often with padding at the elbows.
Step 4 - Coaches
When coaching a team, there are a couple of equipment purchases you will find helpful. Small cones are available at any soccer shop, and come in handy in a number of drills. You'll also need a batch of pennies (mesh practice jerseys or vests).
Once you have the basic soccer equipment, consider adding to your gear. In addition to uniform shorts and jerseys, many players wear compression shorts or "sliders." Some players wear soccer headgear, designed to disperse the impact of the ball. It's helpful to have an air pump to keep your soccer ball inflated. Last but not least, most players have a soccer bag designed to easily carry most of their equipment.