It might help to restrict sweets, sodas, juices, etc.
In the 3+ years that I have been on this forum, I have never seen a post where the poster had a child with ADHD that had any real noticeable changes with any herbal supplements. Of course, healthy food is always important.
If you want other ideas to help your child, try reading - "The ADD/ ADHD Answer book," by Susan Ashley. Best Wishes.