I have done an earlier an earlier run doing this scenario. I found a great mountain area with lots of caves. The caves had dirt and trees in and around the entrance that I could collect. You can plant trees in deeper cave but I tended to plant them at surface entrances where there were caves or deep openings to start. Once you have the ability to large scale mine, and have lanterns, then trees become easier to grow completely underground. You are going to have to go topside to get your seeds for growing food. I restricted myself to 1 day on the surface a month. You can chase, capture, or lure animals into your caves to farm them.
I also tried a mixed run where I was trying to be more authentic to some Dwarf fiction by finding a very large mountain range with deep open areas in and around them. That is where I farmed and herded. I built great defensive walls and towers to defend my kingdom by connecting the different accessible areas, like in traditional medieval fashion. I would punch out and build platforms in strategic spots to build catapults and ballista. I used old Warhammer Fantasy art and its like for inspiration.