The first and most important thing to focus on is that you and your partner are fit and healthy. Above all else, your wellbeing is not only crucial to the baby-making process but also to your mental health and your ability to be active parents, once the baby does come along. Being significantly over or under weight is going to have negative impacts on your health as well as fertility, so this issue needs to be addressed. Regular exercise and eating food that is good for your body is the best thing that you can do to kickstart conception. You will feel better, your body will be functioning more efficiently and so too will your reproductive organs. When you eat foods that are good for you, you will find that your body has all of the elements experts say you should have (like folic acid, zinc, vitamins, etc.), and the negative elements (like alcohol, sugar, etc.) are eliminated, simply by choosing healthy foods.
You are the one who knows what your body can tolerate, too. Having a diet rich in complex carbohydrates is not going to be as important for you if you are gluten-intolerant, or it may be a challenge. For someone who is lactose intolerant, you are going to need to source calcium in other foods or supplements. So there is no one size fits all diet to improve fertility chances because everyone is different, and you need to remember that! Finding your own overall wellness is the first step!