My first playthrough, i'm using to just run around on.

I need to know what I should do or who should I join. (Not NCR already on that)
So any SPECIAL ideas or tag skills?

SPECIAL and tag skills don't really factor into which factions you can or can't join... so it doesn't really matter in that regard. Only for the type of character you want to play. If you plan on going Legion, though... maybe playing a female character is not such a good idea, given what the Legion does with/to "their" women.

I'm going for a stealthy spy-type this playthrough, so I tagged small guns, (my combat speicalty - suppressed weapons) science and lockpicking (for infiltration purposes) and spend most of my level up skill points on sneak. My SPECIAL started at 5454T65, and I took four eyes and small frame (so +2 to P and +1 to AGL, for most practical purposes). Stealthy character with big brains for max skill points. Obviously, a crappy build if you want to specialize in close combat or big guns, but I don't. I'll be teaming up with Boone because he's also a sniper-type, and taking ED-E as my robotic companion, and both their styles and perks compliment the silent-death-from-a-far combat style I'm going with, but again, if you like a different play style, you'll want different companions too, most likely. But again, if you're planning on siding with the Legion, this will not sit well with a few of your potential companions, so that might add a restriction or two as well.

After my first one I'm going to play on hardcoe with a Tank-type build.

I would try a Melee build, but I just don't have that kind of patience.