undead is a pure attacker choice. The build strat shouldnt differ much from other attackers, use lots of rax/TGs you would be fine. I would also incorporate some homes, seeing that u should be making a lot of exchanges, and thus likely to be underpop a lot.
The most important aspect of playing undead, is knowing how to convert elites. Primarily, note that oversending diminishes conversion rate, so you ought to find targets you can barely break at your NW exactly. The NW range to look for would be 90%-110% of your own. If you are running super high offense (which you should), you should even be finding gnome turtlers to break. Dun let other noobs tell you its not possible to achieve 100 opa with specs. Undead generally have low NWPA, so if you are at same NW with a gnome with 180+ NWPA, you prolly have more land. Which means, if say you are at 150 NWPA, you should be able to break that gnome with just 80 opa.
Another important aspect of undead is off/def ratio. Suicidal is good. It incentivises people to retal you, so you make lots of exchanges in land. That keeps you from outgrowing your KD, and plays on your primary advantage, your immortal offense. But in war, being the lone suicider gets you killed fast before your KD can exploit the opportunity. Hence, undead plays best in a full-undead KD, where most if not all run low def and super high off just like you.
My KD ran undead with 25-30 dpa raw beginning of age, using rest army to offense. We won all our first 4 wars, so i find the strat pretty slick. Of cos, knowing when/how to chain is important to utilising all that offense.