Puppy eating enough

For the first couple of weeks, Lucy was eating very well...but lately she has been picky. She eats, just very little...so I am not sure what to do. I feed her the canned IAMS puppy food and she eats no more than a tablespoon at a time. I try to feed her 3-4 times per day. I am just not sure how much a 1 pound dog should be eating! I know it is my fault that she is being picky, because she didn't act like this until I gave her some "people food". I am gonna go to Petsmart tomorrow and buy the gravy for dogs and hopefully that will incourage her to eat. She is very active and plays a lot, so I am probably worried for nothing, but I was just wondering if yall think 1 tbs per meal is enough??