Depends on where you are shooting (indoors / dark relative to sunlight) and whether your 18-55mm lens is image stabilized
Food does not move. You only need one (or at most a few) shots. You can usually fill the frame with the subject, so 18 Mpix is enough. So, food photography is the easiest photography to take when you consider the functionality of the camera.
One of the advantages of many 18-55mm lenses and cropping cameras is that they allow you to reach fully acceptable macro distances. Not good enough for insects, but certainly good enough for food.
However, if you photograph your food indoors, you will find that the interior lighting is very dim. It is darker inside than you think. So your photos may end up being shaken if taken without image stabilization at small apertures of the 18-55mm zoom.
So, if you find your photos are shaken and your 18-55mm is not a stabilized lens, replace the old 18-55mm lens with an 18-55mm stabilized lens. ;picture. I suggest going for (1, 2) STM versions of the lens; It is a much better value as it can shoot videos without autofocus ruining the audio track. It also doesn't look like a child's toy when in focus, which is an advantage. The older STM lens has better maximum magnification, so for food photos, I would prefer the old f / 3.5-5.6 STM to the new f / 4-5.6 STM.
If you want to get shallow depth of field effects for your food photos, add the 50mm f / 1.8 STM lens to your kit. Its improved close focus distance compared to the old 50mm f / 1.8 II lens allows for easier shots.
Your camera is not too old. Its resolution is quite good. Its low light performance may be slightly dated, but not too much. Buying a better camera can be a step backwards, such as a full-frame camera is worse for taking pictures of close-up subjects because of its large sensor, and the camera full-frame photo usually does not accept cropped lenses (or if so, with reduced resolution), so you also need new lenses – the best zoom lenses tend to have distance slightly worse minimum focus than inexpensive EF-S 18-55mm lenses.
So my suggestion is the "EF-S 18-55mm f / 3.5-5.6 IS STM" lens (but only if your current 18-55mm does not have a stabilizer), and the "EF 50mm f / 1.8 STM" lens. You should expect to pay between $ 300 and $ 400 for the two together. In particular, stabilized zoom lenses from 18 to 55mm can often be found very inexpensively as second-hand items (less than $ 100 where I live), so even $ 200 to $ 300 might buy you a good food photography kit. If you buy a used 18-55mm, make sure that it is a stabilized image version. If you buy a used 50mm, make sure it is the STM version with an improved minimum focusing distance.
The easiest way to improve the colors and contrast of all the photos you take is to use a lens hood. Fortunately, EF-S 18-55mm lenses accept an EW-63C petal cap. The 50mm lens accepts a slightly worse ES-68 circular cover. Make sure to buy both if you find that your colors and contrast are lacking.
Once you have the most suitable lenses and caps for them, if you want to enhance your photos even more than what the lenses can help, take RAW photos and download Canon Digital Photo Professional. Use the Digital Lens Optimizer function and learn how to correct the exposure and make other settings.