I always used about a tablespoon of fresh garlic per gallon of milk - more is for serious garlic fiends, and less is for people that just want a hint. Easy to measure that way, since I would just grab a bunch of heads of garlic, peel the cloves, and whizz 'em up in the food processor. Freeze them in 1 tbsp lumps, and pull out as needed for cheese (or anything else, for that matter). No fuss, no muss - except the eye-burning if the garlic variety was a strong one
That will probably get you to a good happy medium and you can adjust on your futures. At one time I'd gone up almost 6 heaped tablespoons in a 3-gallon make, and that was too much even for me, by the time the cheese finished aging - you couldn't taste anything BUT the garlic.
(I should note that these were all cheddars - so I was taking the 8-12 month aging time into consideration, having heard that garlic - fresh or otherwise - can get bitter over time. So maybe you could pile on more that a tbsp per gallon after all, in a short aging cheese. Although if you added roughly 12 cloves of garlic, that seems to be less to me than my 1 tbsp smooshed. Ah, 'tis a puzzlement.)