MGS 1 is honestly the hardest in the franchise (unless you have glitch copies of MG1 and MG 2) because of the more strict stealth mechanic. Yes, really good players can get through it with 100 % stealth and minimal kills, but my point is it is less forgiving with mistakes. Guards Cone of View is super sensitive and the minimal health bar is a pain when do you get spotted making it pretty much insta death. However, as someone who has played all them religiously a tip I can give you for MGS 1 is as follows
1. The judo flip is your friend, you dont have to choke, pummel, or shoot annoying in the way guards. The flip will give you enough time to drop a guard and get to where you are going.
2.Every boss has a exploitable weakness that a lots of people still don't seem to know
a.The waves of guards after the DARPA chief dies, you can save ammo and health by letting Meyrl kill em all. She will hesitate at first but she will eventually gun down all waves. If you want to speed it up flip a couple of the soldiers so she can take em out quicker.
b.Ocelot is literally simple as playing aggressive during his first reload because if you hit him he can't reload and you can take him out before he even shoots again if you are quick enough.
c.The tank on the way to the nuke storage, the treads can be knocked out with claymores as well as grenades. This is helpful if you are having issues with hitting him with the nades.
d.Gray Fox is pretty easy, so not a lot to say about him other than you can use a gun during the final stage of the fight
e.Mantis is stupid easy if ya know two simple things. First, when he goes invisible whip out the FAMAS and find his location using the FPS view (don't forget to out your controller in the 2nd port) and spray in his general direction. Second, when he does his attack where he fly towards you spinning chairs duck and when he is in the center with you stand up and punch him a few times to shave away his HP faster.
f.Sniper wolf the only thing that can be said about it is you find her location by keeping an eye out for her breath
g.Not much of a boss fight but the 3 guards on the bridge have an easy no damage solution. Get the PSG-1 and shoot them each 3 times and line your sights on the the first one on the left and tap the trigger over and over the other two will run into your fire and die.
e.Hind D, just stick near that center piece of cover and hide after each hit with the Stinger, and you can also track Liquid through the building giving you and insta shoot when he reveals himself
f.The stealth guards on the elevator are pretty simple, go to the bottom corner of the elevator and spray them down with the FAMAS until ya kill em
g.Sniper Wolf second fight is IMO the easiest in the whole game. Simply go and hide behind the rock on the right side of your side of the trench and use the Nikta to kill her
h. Raves is your pac man enemy, simply set claymores around the corners of the containers and enjoy the show
i.Elevator surprise attack is simple as stun the with the stun grenade and snap their necks one at a time while they are stunned
j.Rex is a classic follow the pattern boss. Fire rocket, run towards to avoid missile, run from to avoid laser, and repeate for both stages.
k.BEAT HIS ASS SIMPLE
Congrats, if you read this whole thing you are well on your way to beating MGS 1 no problem if ya need any hints or tips for the other games send me a PM
You should really only play the essentials for the story so far. Play Snake Eater, then watch the movie versions of Portable Ops and Peace Walker. That simple.