Congrats on the upgrade! I have had mine for about a year now and its a beast, but you definitely want to protect that investment. First thing I did was slap on a ULBTER Tempered Glass Screen Protector for Canon R5. It is basically super cheap insurance against scratches on that nice flip out screen and the top LCD. Also, dont really trust the thin strap that comes in the box. I switched to the Peak Design Slide Camera Strap Black because the anchor system is rock solid and I never worry about it snapping or dropping the gear. For the cards, since you already have CFexpress, make sure you get a reliable reader like the ProGrade Digital CFexpress Type B and SD UHS-II Dual-Slot Card Reader. I have seen too many cheap readers overheat or corrupt files mid-transfer. Stick to the name brands for anything involving your data or the cameras safety, honestly.

Adding my two cents... are you mostly doing video or stills? For mounting, the SmallRig Camera Cage for Canon EOS R5 2982B Aluminum is a solid budget alternative.

Saw this a bit late but congrats on the R5! I am gonna go against the grain here and say skip the cage for now. Unless you are doing heavy video, its just extra weight and money you dont need to spend yet. I have found that keeping your sensor clean and your power levels up is way more important for your first big shoot. Grab a Giottos Rocket Air Blaster Large and a VSGO Camera Sensor Cleaning Kit for Full Frame Sensors instead. Way cheaper than a professional cleaning later. Also, since those new Canon batteries are so expensive, I suggest getting an Anker 737 Power Bank PowerCore 24K. It supports PD charging so you can top off the R5 during breaks. Honestly saves so much money compared to buying a bunch of spare LP-E6NHs.

To add to the point above: MythWeaver is spot on about power being your biggest hurdle. Unfortunately, I wasted a ton of money on the official Canon gear when I first got my R5 and it was honestly a letdown for the price. I had issues with the official charger being slow as dirt while on a wedding shoot, which was a total nightmare... I definitely suggest looking at some solid budget alternatives rather than the high-end stuff:

• BM Premium 2-Pack LP-E6NH Batteries and Dual LCD Charger
• Neewer Metal L-Bracket for Canon EOS R5 The L-bracket is way more practical than a full cage if you arent doing serious cinema work. Plus, those BM batteries have been just as reliable for me as the originals for a fraction of the cost. Just make sure whatever third-party battery you buy is actually the NH version or you wont get that green H plus icon for your fastest frame rates. Ask me how I know... lol. Its those little things that really matter when you are out in the field and things get hectic.

Saving this whole thread. So much good info here you guys are awesome.