Not knowing what your space looks like...
- The kit lens at 55mm F4.0 should do. Faster aperture than that and parts of the image will be out of focus. Shorter than 50mm you'll risk barrel distortion.
- The 60mm is a good option, but I'm not sure that macro is needed. For social media, context is key in an image. Super close-ups aren't always flattering in any case. For use around a restaurant (think table photos, team photos, cool pics that seels the vibe) a fixed focal length that long could also be limiting. So I'd say kit or if your budget can stretch the 16-55 will be ideal. Of course for pics around the place where light isn't great the 16-55 will trump the kit lens. But the lens has stabilization!
- 50mm F2 will also be a great option. Small, good at low light, sharp, close focusing, etc. But again, when taking other shots it COULD be limiting.
What I would suggest is to earmark a dedicated spot where you take plate photos and invest in some form of light or flat lay there. Similar looking images will trick the mind into immediately recognizing it as yours. So when scrolling through a feed a user will instantly know it's yours. It can also form part of your "brand".
Also with a flat lay, you can have a dedicated surface that photographs well, you can have one or two small lights that can switch on and off easily for pics (Aputure MC comes to mind), and even get a mount for the camera that keeps it in place and will allow you to use the timer to take a photo to avoid shake. That will also be a great snap-and-go scenario. No need to find lights, a clean surface, "where did I put my camera", etc. Have a dedicated space and you'll DEFINITELY use it more often.
Here's an example:
https://www.instagram.com/capeofgoodwine/?hl=en
Flat lay will also afford you the opportunity to add a wine bottle as a pairing suggestion and some other items as props. (Tip: include a plant or something with height to add depth to the image. Example:
- https://www.instagram.com/p/CGuumOepRGf/
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Keep in mind that for social media it's important to sell the sizzle and not the steak! Lifestyle over product.
Lens: 16-55 would be my call. Then 18-55. For purely food, I'd say 50mm F2.
To add: food photography is tricky to get right. Including context and being too zoomed in will avoid that to an extend.