A long prime lens is great for field sport. A good starter long lens would be a 300mm f/2.8 prime. They are expensive, but sometimes come up for sale 2nd hand. Keep an eye out. They are a great investment. But the bigger the field, the longer the lens you would want - 400mm f/2.8, 500mm f/4, 600mm f/4 ... or more, by adding an extender. But, remember, an extender also alters your maximum aperture by a factor too.
For close in action or where you can get up close to the action, then a medium telezoom lens, like the 70-200mm, is great.
Getting closer again, for events like boxing, where you are right at the action and it doesn't move too far away, then a short zoom like the 24-70mm lens is great.
Some events you are right on top of the action, or you want to get a larger scene in. Then you want a wide angle lens. 16-35mm, 17-40mm, etc. It will depend on your camera body, what lens it can take and how wide you can go. You can also use a wide lens for dramatic effect, taking crowd shots, overall stadium shots, etc.
The one lens in almost every sports photographer's bag would be a 70-200mm f/2.8 lens. You can also get the f/4 version, which is much cheaper, but for low light conditions, the f/2.8 version is more important. Buy once, buy right.
Another important piece of equipment, especially for the bigger lenses, is a good monopod. It can help hold that weight and also give you more stability.
With your lenses (or camera body), turn OFF image stabilisation. This is not needed, and can slow down the focus of your camera. Unless you are panning, it is not of much use for sports.
Your memory cards are also important - buy reliable brands, from a reliable source. Sandisk, Lexar, Transcend, Kingston, Sony, Samsung, etc. Buy quality fast cards. While price is important, a cheap card can cost you more in the end, especially if your images become corrupt. I've had it happen.