The herb periwinkle (Vinca minor) is my absolute favorite. Other herbs that can help with memory and concentration include gotu kola, sage leaf and ginkgo biloba. Lecithin granules are also highly recommended to both build up nervous tissue and the neurotransmitter acetylcholine.
My oldest son was diagnosed with Attention Deficit Hyperactivity Disorder and was on many drugs for many years, mostly Ritalin until he took himself off it at age 16. I wasn't at all into health back then either. But once I got into health I learned a lot about ADHD and ADD help with natural things and one of the best was fish oil and lots of it. We are all fatheads and our brains need lots of oil to function at peak efficiency!
I agree fish oil is great, but keep in mind that it also contains a lot of vitamin A, which can build up and become toxic to the liver if high doses of fish oil are taken. Vitamin A is also very hard on the bones at relatively low levles. So the fish oil extract EPA/DHA is a much safer choice and is the active components in fish oil for the brain.