Are these for topical application or internally? I don't see oatmeal being good for acne internally, but a topical application is known to work decently.
Good foods internally are basically the paleo diet (though watch out for meats, as most are fed a grain-based diet or accumulate environmental toxins in their tissues).
Specifically, and in order of helpfulness:
Broccoli/other green vegetables
As far as topicals, I've used yogurt, honey, cinnamon/nutmeg/ground cloves, matcha, lemon juice, and egg, and while I haven't found that they improve acne, they seem to improve skin quality/texture.
For supplementation, I've used zinc in the past with some success. I've also found that niacin is useful, but you have to be careful with it, and the effect is often temporary. Fermented fish oil/butter oil blend is also very nice for skin texture, teeth, and eye whites (my eyes were practically glowing in the dark on that stuff, so sexy). The oil blend has vitamins A, D, and K, so it makes sense that it would be useful for skin.
Note - I would say that olive oil is not actually good for acne. It has a 10:1 ratio of omega 6 to omega 3 (so, at least 3x more omega 6 than is ideal). It's certainly better than other vegetable oils like soybean (stay away from that stuff), but overall I would say it's neutral at best, if not very slightly detrimental.