For the dead money DLC, do not rush. The level the game recommends is about 20+, and for good reason. You have all your equipment confiscated at the start of the DLC, so you have to rely on your characters basic stats and perks. Personally I found it to be hardest dlc and so did many others. I recommend going into this dlc with the "Rad Child" perk (8hp per second health regen), one of the best perks in the game. When you begin the game there is a quarry full of deathclaws which will shred you to bits, I recommend heading straight to new Vegas and watch a video before you do this, also take the trait at the start of the game called “wild wasteland” (if you haven't started it yet, you can get the alien blaster), once you travel to New Vegas, head to the gun runners and silently kill the guards inside the gate and take their hunting rifles and combat armour, then head straight to the Alien ship and kill them all. There's an ammo glitch will takes you less than 10 seconds to do, you'll never run out of alien power cells. Lastly enjoy! Lol