How deep is the mantel? That makes a big difference. Natural garland if you need it for a party or for two weeks. If you want it up for a month, do faux.
IMO the led flicker candles look really convincing in cut glass or any glass with a lot of texture.
These are maybe not as textured as ideal but they are cheap and come in a set. Put them randomly on the mantel, like maybe three in a group and then the other three each alone going away from there.
https://a.co/d/eDXgomD
Or copy Cassiopeia and put the extra one with a friend. Put a led tea light in each one.
Then wind the garland around the candles.
Pottery barn has a ton of weighted stocking holders. Pick some you like. Divide your mantel into thirds, and center the row of stockings in the third on one side or the other. If you have too many stockings, just start moving the group towards the center once you hit the side edge.
IMO that’s plenty. But if it doesn’t feel like enough, you can add pinecones, berries, etc. If you want natural materials and you’re loaded, go to American plant food! They will have a ton of berries and stuff you can pick up with your garland.
If you want further inspiration, UK homes and gardens always has fun Christmas decoration photographs that aren’t boring.
If you decide you’re into that “more is more, heavily ‘decorator’” aesthetic but you just don’t know how to do it, you can buy whole tablescape kits from Mrs Alice. You could easily repurpose one for a mantel!