I play rammus im kinda new so IDK what some champs use. So I was wondering if someone could give me a list or a site so I know how to gear my rammus for tanking against a team.

Thanks in advance. Hope I explained that right.

If you look at your spells you will see a number in parenthesis. If it is green, ability power will increase that number. If the number is orange, then attack damage will increase that number. That in a nutshell is how to tell what stat your character will want over the other. Of course, many heroes use a combination and you have to use your own judgment or read forums/strategy guides to see what is usually the most viable option, many characters have many people that will argue one side over the other so there usually are multiple paths for each character. If you are using Rammus, his passive makes his attack damage increase with stacking armor. So if you get items with armor on them, you will also gain an increase to attack damage. If you type "rammus" into the search bar at the top of the forums you should be able to find some strategy guides from players that should help you in the right direction. I hope this helps.

Best way to learn this is to play each champ, even in just custom matches with yourself, learn how they work, and what they build to get powerful.

Easiest way to learn this in a fight is to pay attention to items. Things like people building a Doran's Ring or Doran's Blade first thing is a dead giveaway that they are a high damage dealer that focuses in that items damage type. Things like Infinity Edge and Rabadaons Cap are dead give aways of High-AD or High-AP dealing champs.

And finally, when you die, click on the death recap and see what damage type did the most damage to you.

Ideally you'll want to build a combination of both resist types. Aegis of the Legion is a fantastic first tanking item to get just to build some initial resists for cheap while you try to figure out what to push next. Plus it helps your whole team which is key for a tank.

Every time you die during a game, check out the death stats. It tells you who did how much damage with what spell and with what type of damage. As soon as you find that out build accordingly. Or, simply look at the items they are carrying.

Press tab and look at the scoreboard. The items they buy will match with the damage type they're focusing on. This is really the ideal way to do it as you won't be caught off guard by AP Trists or other unusual builds.

Also remember that a combination of health as well as resists is usually the best way to build up survivability. As you encounter different champs more often most of them will be using skills which deal magic damage (eg. Ryze), apart from some (eg. renekton, whose skills deal physical damage.) You will also begin to notice some champs deal the majority of their damage by attacking normally (auto-attacking; eg. Trundle, Udyr); these will be dealing physical damage to you (but watch out for items like Madred's Bloodrazer as this makes your auto-attacks deal additional magic damage.)

You can read up on different champ abilities here
It's otherwise quite hard to know for sure which champs are dealing what kind of damage unless you actually play them.

Also hit tab often throughout the game to see what everyone is building - it's a good indicator of what kind of damage they're going to be dealing, as well as looking at death recaps.

I always recommend getting an aegis to help your team out if they are particularly squishy and you're up against a tough team. And remember that if your opponents have a lot of CC, you'll probably want to get Banshee's Veil or Quicksilver Sash.