i have been thinking about doing an NCR ranger-styled character, and starting to wonder what the build would look like.
What skill would need to be tagged and perfected (100) what perks to be taken and gear to use?

Character would be female for some reason

Melee, Survival, Sneak, and Guns should be your priorities, with the Cowboy perk and two ranks of toughness. Take Cannibal if you want to be a real hardass. Wear either Ranger Patrol armor or the regular ranger outfits, and a Rattan cowboy hat. Use a Ranger Sequoia as your sidearm, an Anti-Materiel Rifle as your main gun, and either Chance's knife or Oh, Baby! as your go-to for CQC.

Stats would favor Endurance and Agility above all others, likely. With third place going to either perception or intelligence. Might even strike a point out of charisma to up something else.

Skills would favor Guns, Explosives, Survival and Sneak. Unarmed and Repair are also probably rather high. As for perks, it's more up in the air. The "Tag!" perk would net a fourth tagged skill. Toughness a few times for certain. Rapid Reload, quick draw, lead belly, finesse, silent running and nerves of steel would round it out. Intense Training a few times as well. Perks like Cowboy, shotgun surgeon or any of the other weapon damage perks are entirely up to the individual, but I'd avoid them. Rangers are supposed to be supremely deadly with any weapon they lay their hands on, but specialists are certainly doable.

Remember, Rangers aren't in-your-face brawlers. They strike first, fast and very hard, the get the hell out. They can stand and fight magnitudes better than any other mere trooper, but using them like that is a waste. Rapid movement and silence is how they roll. They also work in either a very small group or alone, so survival skills and raw out endurance are their defining traits.

When in doubt, pile on more hit points. Rangers just don't quit until they've been out down hard.

As for gear, one or two ranged weapons of choice (Gobi Rifle and Marksmen Carbine are awesome choices for main arms) and one melee (I prefer a combat knife.) A few grenades if you're feeling perky. Armor is a no-brainer. Either Ranger Patrol Armor, or Ranger Combat Armor.

Load the hell up on ammo and water. For soldiers in the desert, those two things decide life and death. Food isn't really a proplem, as a healthy human can go for around 30-40 days without food if need be, and whatever is lacking can be taken off the land in FNV. Ammo is the real important one, which is why it's smart to limit yourself to two types. 5.56 is ludicrously common, as is .308. Surprisingly, the "bulk" ammo is going to be your best friend. It may be dirty as hell, but with a high enough repair skill and ten minutes of sauaging, you can make repair kits. Stim Packs are awesome, but water is more common and more useful. RadX and Rad Away are also must-haves, especially if you end up drinking from a river (pretty common, really.)

Healing is'n't really that much of a problem, since if a Ranger is being played right, you won't be taking much -if any- fire at all. It's why I love the Marksman Carbine. It's a great sniping weapon, but if things get close, it can rock and roll just fine.

All that said, my gear loadout is built for endurance.

Main: Marksmen Carbine.
Special: Gobi Rifle
Reserve: That Gun
Combat Armor, Slave Scarf and Tortoiseshell Galsses.
Over 1200 rounds of 5.56, nearly half of which is "surplus" ammo. 250 .308 rounds. Six frag grenades and a combat knife.
20 bottles of Purified Water
40 Stimpacks
15 weapon repair kits.
Binoculars

what about a speech of around 60, i mean the natural after the other priority skills are up, to get help for the NCR for Hoover Dam? or spending a few points here or there on it?

and besides I'm not really planning on this character until another playthrough

A ranger should have a fairly high speech and charisma IMO. Go and have a chat with Chief Hanlon, you'll see.