I want to play on hardcoe, but I wanted to add some other things to, make the game more realistic. What would you guys recomend me doing, I'm more used to things for Oblivion and Skyrim, this being my first try of doing it on Vegas. From what I understand the Legion, forbids stims meaning no stimpaks, but how I'm supposed to survive with only healing powder?

This is where having the First Aid skill would be incredibly useful. I guess use food and water to heal. Truthfully, I rarely use stimpaks in New Vegas, mostly because of how easy they made Fallout 3. I just got used to ignoring them, so it carried over to New Vegas even though they aren't as overbalanced there.

Max Survival skill and get tons of food and stuff, also craft tons of Healing Poultice, cakewalk.

Eating food to gain health, is unrealistic so thats out the window. So I wonder how I'll be able to, stock up on healing powders.

I'd suggest playing without using any chems (including radx, radaway, and stims) or drinking any alchohol, ever, I'd also advice never using a doctor or a merchant, makes it extremely fun playing, and with the pain in the ass to make, fiery purgative, being the only source of lowering your radiation it'll truly become an emergency only thing to do drinking radioactive water and eating radioactive food.
I'd advice entering Honest Hearts early, it got massive amounts of the most important ingredient for a legionary, cave fungus.

Why not visting a doctor or merchant? On hardcoe mode only doctors and doctorbags, can healed crippled limbs.

Trying to play as a Legionary, yet keep a realistic tone? Its easier than you may think.

Your going to basically avoid any form of chemical medication. Sticking with the survival skills healing areas, such as healing powder, bitter drink, etc., you can make quite a bit of progress in the medical area with the lack of stimpacks.

I would also recommend sticking with light armour, as for if you have a few DLC's, you'll find quite a few nice perks to assist with speed & damage.

Only healing life stopping things such as broken limbs, you could only see doctors & avoid doctor's bags. Though, cutting back on everything aside, you can take it a step closer to avoiding doing business with NCR &/or NCR affiliated merchants to have an RPG aspect of boycotting their goods/services.

Any tips for finding good areas, for ingredients other than Honest Hearts? I should mention that I do have, the Ultimate Editon so DLCs, aren't a problem. I was thinking of him being a future centurion. Hmm I believe cannibalism gives rads, until I get the dine and dash perk, but I could get rads from other things, how would I deal with them?

How so? I mean healing as fast as stimpacks do is already unrealistic, but if a well-nourished and mal-nourished person both sustain injuries, you can bet the well-nourished guy will heal up quicker.

At any rate, Legion playthroughs are fun. No chems (Stimpacks, RadAway, Rad-X, any drug type), food for healing, avoid implants and specialize in melee/unarmed. Guns and energy weapons, contrary to popular belief, are allowed, they're simply not the focal points of the character build. This playthrough is fun because it basically requires the player to hunt to gain healing items (Gecko steak, bighorner steak), it adds all new difficulty to irradiated areas while giving anti-RAD perks purpose and melee/unarmed is actually incredibly strong once perked up. My only suggestion is that you DEFINITELY need good STR and Endurance. This is a not a playstyle for a low-endurance character especially, because you'll need several endurance-based perks to survive some of the challenges one faces without chems and implants. Endurance provides higher Rad resistence, poison resistance, allows your rads to naturally go away (basically essential perks for this playthrough OR you avoid radiation like the plague) and provides you with more health and a way to regenerate health over time.

What I meant was people dont eat food, after getting shot or stabbed, thinking it will give them health. Well for my special my strength, agility, and endurance are all 8 while everything else, is 4. I tagged unarmed, melee, and survival, along with have the traits heavy handed and skilled.

Good choice. I had a Legionnaire character that sadly died to an NCR hit squad at level 39 or so, but he was similar. As I recall, he had Heavy Handed, Kamikaze, then his special was:

10
3
10
3
4
7
3

That was an incredibly fun playthrough.
You'll wanna avoid irradiated areas until you get a perk that gets rid of Rads, I think the first being level 16 or so (reduces them when you sleep). There's later ones that reduces rads slowly and the like, too.