A helpful thing you can do with an above ground fortress is first, embark on a flat region. As flat as possible. Its best if its completely flat.
Then around the entire edge of the map construct drawbridges. Leave a gap for the entrance. Link all drawbridges to a lever, and pull the lever to raise them. Then deconstruct the lever. This will limit access to your fortress via only a single path, allowing you to concentrate your defenses there. All visitors to your fortress, both friendly and hostile, will arrive at the only accessible tiles on the edge of the map.
While you could of course build a huge pile of weapon traps and fill them with giant discs, that is just unsporting. Go with a large dwarven military instead. Build a barracks at the entrance, and assign your military to be active/training in the barracks. No traps, no tricks, just dwarven steel to keep your fortress safe. Massed marksdwarves, as in 60+ marksdwarves all in a blob, can unleash enough firepower to kill almost anything. More dakka always works. If its not working, you need more dakka.
Then build a thriving city.
Clay or glass is probably ideal. If you have sand or clay then you can build infinite blocks from only a single source tile. Magma provides all of the energy needed. If you don't mind green buildings, glass is probably best, as you can make other things out of glass. By building tens of thousands of glass blocks you'll have a lot of legendary glassblowers, who then can make masterwork glass furniture, pots, doors, and even large weapons for weapon traps. Glass isn't nearly as sharp as steel, but a masterwork giant glass disc is dangerous enough.
If you want to build entirely out of wood then you'll almost certainly have to go underground for more wood. Build underground tree farms to supply the wood. Surface wood cutting will simply not provide enough wood. Consider that saplings will be trampled, and ground will be used up from the construction of buildings and walls. If you want a uniform color of the wood, set up a custom reaction to turn a wood log into a wood block of some type, so you can process all wood blocks via some form of lumber mill into uniform blocks for construction.