You need to use a skin care regimen to keep your skin clean. It took me many years to find one that worked for me. I am an adult and have acne. I use Murad. Now you cannot even tell I have acne. I do occasionally get a zit or two, but that is it. Murad works for me but others have had luck with Pro-Active. Pro-Active was too harsh for my skin (I have sensitive skin).
What you eat does not usually affect your skin's acne conditions. I suppose it could if you have a gluten problem or something similar. Drinking lots of water is always good for you though.
You need to keep your skin clean and most importantly...DO NOT PICK OR TRY TO POP the blemishes. I know it is really tempting, but it only makes the problem worse and can lead to scarring. Keep your hands away from your face as well.
If you want to try the Murad or Pro-Active, you do not have to get them on-line; they are available at some beauty supply stores like Sephora and Ulta.