I've been shooting my kids doing sports for the past 15 years. I've gone from kindergarten T-Ball & Soccer up through High School Football, Rugby, Basketball & Water Polo.
My advice to you is this: Don't let your gear get in the way.
Sure, A great body with high FPS and pro-level Auto focus is ideal.. And who doesn't want a 70-200 f/2.8 with blazing fast focus motors and chart-topping sharpness? But not everybody can afford that.
My advice would be:
1) Pick your system based on what other people use. Right now... that's Canon and Nikon. I'm not bashing Sony, its a great system. However, You'll never see any professional sports shooter using anything but the big 2 (see #2). Sports 'level' equipment is expensive!!! You'll have a better chance buying good quality used Nikon & Canon gear. There is just more of it floating around.
2) Study pictures other people have taken. What gear are they using? What where the camera settings? How did they setup the shot? There are 1000's of blog posts talking about shooting sports with Nikon and Canon gear. 1000's of reviews of lenses used for shooting sports. Start googling!
3) Learn the sport. If you know whats going to happen you'll know where to be. I've seen amazing pictures taken from entry-level gear because the person taking the picture knew where to be.
4) Shoot Raw. JPG's are great for Sports Illustrated but RAW lets you get the most out of your gear. Shooting RAW lets you bump up those shadows to see inside the helmets. It lets you get more from your camera.
5) Practice, Practice, Practice.
To answer your question on gear...
The ideal setup would be a 'high end' crop sensor body (Nikon D7100, Canon 70D) and a 70-200 f/2.8. The crop sensor gives you more 'reach' then full frame.. for example: Nikon 300 f/2.8 = $5.7k.. A 70-200 f/2.8 Nikon on a crop body gives you the same field of view (200mm x 1.5= 300mm) for $2k).
It really just depends on what your budget is..
Some examples on how you can bring out faces from the shadows when you shoot raw.. Most of these pictures where taken and noon (full sun).