Google shopping ads are you frenemy, learn to love them and be very afraid of them.
When it comes to consumables like supplements. Text ads suck ass. Google shopping ads can bring you sales as the consumer is able to see the product image, price, shipping details and make a buying decision then and there.
But man you need a lot of negative keywords. Google will try to consume your daily budget as fast as it could.
Some people recommend running 2 shopping campaigns. One with low priority and second with high priority filtering by keywords. Personally, this strategy hasn’t worked out for me so well.
My advice would be start shopping campaign for a single product. It will take a week but you will identify all negative keywords. Allow this campaign to get some data and get yourself some sales before moving on to another product.
Edit- Grammar Correction