IMO one of the first things you should do with any new fortress is put in a 3x3 farm plot that grows plump helmets in all four seasons. Don't worry about planning or aesthetics, just shove it into the soil layers (including sand or clay) you're digging through to reach rock; it won't obstruct dwarf movement so you can even put it in your entrance corridor if you want to. Plump helmets are boring, but they can be essential for survival to a new fortress, and even a mature fortress may still use them as a staple crop.
They grow quickly, so with an attentive farmer you should have a lot of them. They grow in all four seasons, so you don't suffer cyclical shortfalls like you can with other underground plants. They can be eaten raw, no cooking required. They can be cooked into meals, gaining a quality level and providing dwarfs happy thoughts. Most importantly, they can be brewed into dwarven wine. In the beginning, you should not be cooking them. Cooking (unlike eating or brewing) destroys the seeds ("plump helmet spawn"), making you unable to plant more.
As your fortress grows and you come up with enough surplus goods to trade (or enough surplus dwarfpower to gather wild plants), you will probably want to experiment with farming different plants. This is a good thing, different plants have different uses, and you can get more happy thoughts by giving dwarfs their favourite kinds of booze, as well as reduce unhappy thoughts brought on by monotony ("tired of the same old booze"). As you get more space dug out, and can start putting things where you like them instead of in the first available parking spot, you might want to remove that first farm plot and put farms elsewhere. But don't neglect to have a small plot of plump helmets growing. They're simple, easy, and can sometimes be the difference between life and death for your fortress.