I've bought random cheap-ish pannier bags of Amazon and had mostly good luck. As long as they're well made (check reviews, inspect pictures - especially user photos) and compatible with your bike, they'll probably be fine. If you want something really good, yeah, Ortlieb is the way to go.

Cameras, lights, and highly visible protective gear are also good ideas. For waterbottle holders I gave up on cages and switched to feedbags after watching some Ryan Van Duzer touring videos: 10/10, would recommend.

Camera wise: I used to have a Contour Roam but that broke, then I got a Ghost XL Drift, but that broke, now I have an Insta360 X5 and it covers all directions on top of my helmet. The X6 would probably be better because it's lower profile but you can buy adapters that will let older 360s lay flat if you want.

For your repair kit include a patch kit, a tube or two, a bike multitool, tire levers, oil if you have a chain, quick links if you have a chain, and a quicklink tool. If you use a belt drive, a spare belt is a good idea.