Don't feel bad about the purchase, Rammus is a great initiator/tank. The most important tip for Rammus is the early game. A bad early game will screw him over for the rest of the match. You have to keep in line with the opponents or else you won't be able to tank for ****. Also note that he isn't as tanky as Alistar, but he initiates better.
- What distinguishes the good Rammus players from the bad are those that know when to commit, when to fake, and when to run.
- Know when to Taunt first, and when to Powerball first. Taunting first is the best, because you can then Powerball before it wears off so they run slower and can't escape. I tend to roll with Exhaust as well, providing you a THIRD slow.
- Always max Taunt first, but you should have one point in each skill at level 3.
- Until level 6, he's very weak. You have to be patient and not engage enemies unless you have to. You can attempt a first blood with Powerball with an ally, but don't get greedy unless you really know what you're doing.
- The most important thing to do early on is NOT FEED the opponents. Go for last hits, and stay back. Save your mana and use Curl to help with laning so they don't bombard your tower.
- Rammus allows for some of the most varied item builds of any Champ. He has no "best" build, and it will depend on the opponents. You have to plan ahead as soon as you know what the opponents are. Look at which Champs they have that can do damage, and buy the appropriate counter items.
There are three initial builds;
Regen Pendant -> Philosopher's Stone
Doran's Shield + Pot
Cloth Armor + 3 Health Pots + Mana Pot -> Heart of Gold
Beginners should go Philosopher's because you'll have more mana and don't have to be as calculating with your pots. Experienced players should go Cloth first because Heart of Gold synergizes better with Rammus overall. Doran's is kind of a mix between the two. I personally never use it though.
Ninja Tabi or Merc Treads
If you guys are pwning badly, go Swiftness for offensive Rammus
First big item:
* Aegis if you're winning slightly
* Frozen Mallet if you're winning badly
* Banshee's against lots of casters.
* Warmog's against a mixed army.
* Frozen Armor against heavy Auto-DPS
I do not personally recommend Sunfire's. You're paying A LOT for the damage aura, and from my experiences it is NOT worth the money.
I also do not recommend Guardian's Angel until very late game. This should be your last item.