Early-Game Food
Let's face it: you can't eat fruits and berries forever. So how do you set up a reliable source of nutrition? After settling into your new home, now is the time to start working on agriculture and cooking implements so that you won't go hungry during the long night.
Basic Foods
Fruits
To be honest, you don't have to completely ditch the gathering style, but you can make it easier for you to bear fruits of your (lack of) labor. There are two fruits that provide 3 times the saturation & hunger fulfillment: the Biome's o Plenty Peach and Pear. These two fruits stand out with more detailed designs as items, and they are worth bringing to your home to make an orchard with, as they provide as much fulfillment as your starting cooked meals!
Roots
In addition to fruits from trees, be sure to look out for roots on the ground. Despite being used for alchemy, the Ginseng root and the Marshmallow Root are easy to grow and fast to consume, making them quick snacks on the go. For reference, Ginseng only gives half a nugget of hunger & minimal saturation (like most fruits & vegetables); meanwhile, the Marshmallow root fills a whole nugget of hunger and gives more-than-minimal saturation, making it superior for cultivation. To grow these roots, place them on any soil and watch them go from spud to bud in a less than a day!
Agriculture
It's obvious that cooking requires crops, so unless you're solely relying on the gardens that spawn randomly or the fields that villagers sow, you'll need to start tilling soil. Agriculture will be your primary way of raising up vegetables and grains for crafting and cooking. It should be noted that unlike vanilla Minecraft, water is absolutely required to grow crops - you can't grow on dry soil. If you live in an area with limited water (a.k.a. not swamps), make sure to import water from rivers, oceans, or neighboring regions, or just farm in those areas, even if they're a bit away from home.
Chef's Workstation
Once you have your crops producing for you, it's time to make something out of them! The Chef's Workstation will require a chef's hat and some stone to craft, but it is very limited without Chef's Tools, which is just some leather, a stick, a carving knife, and any bronze or higher dagger (or another carving knife). Perhaps a few images of the crafting process would be helpful... Anyways, once you have those in tow, this workstation will help make dishes and prepare ingredients for further processing (e.g. turned raw meat into minced meat, making meat patties, etc.).
Millstone
While the millstone is often used for fiber production, it is also vital in obtaining ingredients like ground meat and flours. While this is the most of the millstone's culinary uses, it serves as an important one, as flour and ground meat are staples in cooking.
Kettle
This is a new cooking implement introduced along with the Chef's Workstation in ROTN 3.0 Beta 6, and is created with four generic metal ingots and one metal fencing of any kind. It will require a heating source in order to work: your best option for now is placing the kettle on top of your furnace, allowing it to draw heat whenever you're using the furnace. This bad boy will allow you to cook a multitude of exciting dishes, as well as some simpler (but just as useful) items like tortillas and hot dogs. The kettle can also be used in the production of Alcohol, as it's required to break down grains into their wort equivalents.