I got the Fly More Combination, and after 6 months am still glad I did. The only part of the package that I wouldn’t have bought is the bag. I would definitely buy the two spare batteries, the prop guards, and the additional set of props, and that pretty much justifies the extra cost of the FMC. So essentially the multi-charger and bag are freebies.
Unless you’re operating only from hard surfaces, like concrete or asphalt, landing pads are a good idea, especially with a quad that sits as low as the Mavics (all of them). There is one MUST HAVE item: landing gear extensions; I got the PGYTECH, which give you an extra inch of clearance, are snap-on/snap-off, and the rear ones nest front ones, so they take very little room in your bag.
When it comes to filters, you get what you pay for. The PolarPro have a reputation for quality and it’s well deserved. I bought a SunnyLife set of filters that was nice, until I realized that I’d have to remove them at the end of every flying session, because the gimbal protector would not fit with filter in place - manufacturer claims it fits Mavic Air...not completely true. I replaced with PolarPro, which is the same height as the protective ring from the factory, and all is great - fits perfectly! The SunnyLife was actually higher, which explains why the gimbal protector didn’t fit. There may be other good brands, but check the dimensions first.
Tablet holders/mounts/shades are a more complex topic...important, but not a “must have now”. Lanyards are very handy if you need a free hand, but are really a part of the holder/mount discussion, since you need to attach the lanyard somehow.