None.Keep in mind that solids fed to babies before they turn 1 are for the experience of eating them, not for nutrition (a subject most doctors know nothing about). Nutritionists recommend starting solids at 6 months; many are now recommending skipping cereal and starting with a bit of avocado mashed with breastmilk (or formula). Then baked sweet potato, oatmeal, pumpkin, pureed peas, etc. Jarred baby food tastes awful, is expensive, and you never really know what is in it. Be sure to avoid the allergy trigger foods. This is not a complete list: before age 1, no soy, dairy, wheat, citrus, egg white, strawberries; before age 2 no honey, chocolate, nuts.
The best book on feeding babies, toddlers and their families is called Super Baby Food by Ruth Yaron. You should be able to find it at your local library. There is some great information on the website: www.superbabyfood.com