It is best to feed your bird the type of food it was raised on, so be sure to find out if that was seeds or pellets. Most breeders include a food sample when they sell a bird. Pellets are more nutritionally complete than seeds and less mess because they do not have shells. However, if your bird was not raised on pellets, it might not recognize them as food and it can be difficult to get a bird to accept this artificial diet. There are several brands of bird pellets available, I recommend Kaytee Exact for Canaries and Finches.
Pellets contain vitamins and more protein than seed, so no other supplements are needed.
If you feed your bird seeds, buy a seed mix just for canaries, not finches or parakeets. Spread the seed in a thin layer in a large dish so it does not get buried in empty seed shells. If you feed a small amount daily, the bird will eat all the types of seed in the mix for a balanced diet. However, it will not hurt the bird to have access to large quantities of seed if you are gone for a few days. Get a vitamin-coated seed mix so you will not have to add vitamins in the water.