Basically, read the title. At what point in time, or what level should I start the DLC? Just got F03 GOTY from Steam yesterday, finished downloading today. What items should I bring, weapons, blah blah. Its my first time playing the DLC, so I have no clue what to look out for XD.

So yeah, what level should I start them at, what skills I should have to make it more fun, what weapons and armor, how many stimpacks, etc etc. Also, I know for Broken Steel I have to complete the main quest first.. ^^.

Thank you for all your help .

I start OA about level 5 or 6. I store any extra gear in the Nuka Cola machine in the subway station, keeping a rifle, that's it. Trust me, you'll have plenty to haul back when this is done.
I start the Pitt about level 15 or up. Again, barely need to bring anything, I bring a scoped magnum, picking up what I find. After you finish the Pitt, you will be able to freely go back and forth between there and the wasteland.
PL is reserved for the mid 20s, though I have gone straight there before. You'll want to bring some gear with you on this one. Flamer for sure, bottlecap mines for definitely sure. You'll have safe storage there, in a couple places. But, and no spoilers here, I would make some strategic saves throughout the main quest in PL, because you might have to reload when you lose stuff too valuable to blow off.
I don't have MZ.
There is a mission that you do, before Broken Steel gets loaded, where I go to the battle in my underwear. With 100% repair usually by this time, I pick up all the good armor and weapons along the way, repairing as I go. Easy way to net about 20,000 caps worth of gear. Though I don't do this anymore. Good luck. Save often, that's all I can say.

I do the DLC with hardly any gear on me, I need all the more room to carry things back. Just take your best death-dealing weapon with you.

This is my order-
Pitt level 8-10
OA level 15
Broken Steel level 20-25
Point Lookout 25-30

I like to do the Pitt first so that I can use the ammo punch for as long as possible.

I havent got MZ either. Most people say you should be high level to give it a go.

It doesn't really matter when.
I started OA with level 2 on very hard. Yeah, it's damn hard, but possible. And you will die, a lot. But you'll start off with a Gauss-Rifle and Power armor at level 6-7!
Same for The Pitt. SPOILER ALERT You don't have your gear for a big part of it, so only HP matters here.

Mothership Zeta is fairly easy. I recommend Level 5+ - get an automatic weapon and you'll breeze through.

Point Lookout is the hardest one IMO. They deal a hell lot of damage (AFAIK at least 35 per hit, DR doesn't decrease it either) and their HP is high as well. Get a ton of Stimpaks and Plasma-mines/grenades and you will beat it too.