It's always best to take you cat to the vet, if it's vomiting a lot. With that being said, if you're cat is constantly vomiting up food, there's a really good chance your cat is vomiting because the Dry Cat food (or wet food) you're giving your cat is bad for your cat and giving it food allergies. Your cat may have a sensitive stomach, so you need to start trying different cat food that doesn't make your cat throw up. Don't buy cheap cat food and expect your cat to not throw up.
My cat was throwing up all the time, I tried different Dry Cat foods (many of the cheaper Purina cat foods) to no avail, that is until I picked up Pro Plan Focus Sensitive Skin & Stomach Lamb & Rice Adult Cat Food
Since then, my cat has not thrown up his food after eating. It’s pretty clear that the constant vomiting was due to the worse dry cat food I was previously feeding my cat.
I think the Lamb and 40% protein in this Pro Plan Sensitive Skin & Stomach cat food are some of the reasons why this cat food has been so much better for my cat. Just read some of the reviews on Amazon and you'll see other people said the same thing, that it helped or completely stopped their cat from throwing up after starting them on this cat food.
So if you're cat is throwing up a lot, I would highly recommend you give Pro Plan Sensitive Skin & Stomach cat food a try for your cat. If that doesn't work, try a different flavor or some other brands that offer sensitive stomach cat food. I also started giving my cat Pro Plan Wet cat food as well.
It's also possible that your cat is constipated, if your cat is throwing up and pooping outside his litter box (or going back and forth to his litter box). In that case, make sure to feed your cat more wet cat food, and 100% pure pumpkin. You can also give your cat a laxatone to help with constipation issues.