How to know if a dog vomiting is serious and should be taken to a vet?

first of all im broke thats why im trying to see if its really serious but im worried about my dog. basically today i got a bit late and found out we're out of dog food so i had to go out etc and she ended up eating late. when she did, she ate pretty fast and ate too much.. had her water and she ended up vomiting less than 3 minutes after. she sometimes also vomits when she drinks too much water. when this happens is it something serious or does normally it happen when dogs drink/eat too much? should i take her to the vet? also, which is cheaper a vet clinic or an animal hospital lol :(

How to know if a dog vomiting is serious and should be taken to a vet?
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