You might want to explain your context.
In some contexts, you could say what it is you do need to know or be able to do. For example, "You only need a basic knowledge of carpentry to..." or "... a knowledge of linear algebra is helpful, but no more-advanced mathematics will be used ...".
In a more generic context, you could say, "You don't have to be a foreign policy expert to understand that the proposed policy will have problems..."
If you're looking for well-worn phrases, you've got a bunch of good suggestions -- I'll add "You don't have to be an expert to..." and "Even a child could ..." -- and should select an answer. If you want something less generic, let us know your context.