Tank of a camera, I love it. Up to 10 FPS and more toys on it that I can figure out.
It's a crop sensor so take that as you will (some like, some don't) but it works great for me.
Sigma 150-500mm f/4-5.6
My first big lens. It's no F2.8 but it gets the job done. This is my go to lens for most track side shots. It has its flaws, it's best not to use it at the full 500mm as the sharpness tends to drop off.
Tamron 70-200mm f.2.8
Perfect for the smaller tracks where the 150-500mm is just too big. Just a great all rounder of a lens for both trackside and portraiture work. A lot lighter too!
Sigma 17-50mm f/2.8
Perfect for when you in confined quarters, whenever that will be...!
Try keeping hold of that 150-500 for a few hours then you'll want one too! Makes using the big lens much easier.
Various SD Cards (SanDisk Extreme Pro)
Using the D500 I can easily fill a 64GB in a day. A lot more if I wanted to.
I like the SanDisk cards as their reader can get up to speeds of 170mb/s. Great for off-loading the pictures.
I do need to get some XQD cards too, but they're pricy.
LG Gram 14 inch Laptop
Great laptop, under a kilo so deserves the name.
Obviously I don't carry this around all day. It either lives in the car or the hotel, or home if I'm not far away.
Lots of walking over all sorts of terrain, you need to look after your feet.
Lowepro Flipside 400
Great bag that allows me to get all my kit in the car in one go.
I don't usually take it trackside with me though. I prefer to just take what I need. The car normally isn't too far away if I really need something.
Lowepro 100AW Utility Bag
Great for keeping all my odd and ends together. Spare cards, batteries, lens/body covers, cleaning cloths, battery packs (for phones) ear plugs, snacks etc.
Peak Design Clips & Pro Pad / Manfrotto QR plates
Great bits of kit for clipping lenses and cameras too you. Can save you carrying them over long distances. The pro pad help spread the weight if clipping the camera with a decent lens to your belt.
The Manfrotto compatible QR plates are great too, makes its easy to swap things around. Compatible with my tripod, mount on the monopod and the PD Clips.
UV Filters are handy for protecting the lens elements. I'd rather replace a Sub £100 filter than a 3 or 4 figure lens. Also carry some CPL filters and will add some ND filters in the future.