Up to you to read this but I'll give you a short comment on all Champions I tried. That means all Champions
Akali: If the other team 'forget' to buy Oracles or so, you will be fed. Very easy to play. Just spam your Ult that can stack.
Alistar: One of the best tank. Need skill to make Pulverize/Headbutt very effective.
Amumu: Very good tank too. If you can get good with his Bandage and time your Ult with the team, he is a pain...
Anivia: I gave up. She is too hard to play for me. But in good hands, she is awesome.
Annie: Just get sure to have your stun. When it is done, she is easy. Just spam your spells and your done.
Ashe: Very easy to play. Hard to master. Anybody can play her and be average/good. Only some can carry with her.
Blitzcrank: If you can learn to use your Rocket-Grab, you will be very usefull. If not, your are useless.
Cho'Gath: Not hard to play. If you want an easy champ with high survive potentiel, pick him.
Corki: You can't be average Corki. You feed or your fed. I'm in the second class so I quit playing him .
Dr. Mundo: Easy to control his abilities but it is easy to over estimate him too. Just go HP and you should be fine.
Evelyn: His skillrate does not depend on you but on how smart are your opponents. Wards/Oracles make you useless or so. Without it, you can be a monster.
Ezreal: Just spam your abilities and you will get kills.
Fiddlesticks: You are good with him or not. Like Corki. If you learn to play him, you will be a living danger.
Gangplank: Very easy. Go critical damage and spam your Parrrley. Your a kind of nuker but with physical damages.
Garen: Hit Q, then W, then E then R. You master Garen.
Gragas: This fat boy can be very good. Only few Summoners are playing it. Fewer play him well.
Heimerdinger: If you like innovation, go Heimer. They change him each patches. Just try to lure opponents in your turrets and be good at aiming your grenade. Very good pusher.
Janna: Any build works fine. She can be used in almost any ways. DPS, Support, Caster and not so far from tank. A good All-arounder.
Jax: Hit all your button and you will own. For the items, he doesnt need any. I personnly buy items by colors for him just to look cool. I will kill anyway.
Karthus: When played properly, he is a real nightmare. Good champion to learn.
Kassadin: If you are fed, you are ridiculously strong. Too strong. But you need skill to play him. You might like this one.
Katarina: Dagger-Shumpo..... Dagger-Shumpo-Lotus-Kill... Dagger-Shumpo-Lotus-Kill.
Kayle: She is like a fat girl to me. I like her as friend but I don't want to play her. Some are very good with her. You can be Support or even AP. A good Kayle is always welcome.
Kennen: A good early champion. An amazing mid-game champion. An poor late champion. Only few are very strong late game with her. You might be one of them.
Malphite: If you learn him, you will be Hulk. But need skills.
Master Yi: All you need to do is farming. When you have your gold, press R and right-click. Let the magic operate. Pro backdoors love him. 0 skill needed. Just be patient.
Mordekaiser: If you want to relax and chat alot, he is for you. Just spam your abilities to fill your shield and that's it.
Morgana: She is a Champion for pros. A noob can play her without feeding. If you learn how to play her, and masterize her add me to your buddylist. If not, don't play her while I'm on your team please. Need skills.
Nasus: Why is this champion still in this game? They need to delete it or fix it. Well if you want a real challenge at being good with a champion, you will find a huge one.
Nidalee: Very funny champion. If you play her well, you can carry your team. Easy to learn but hard to master, like Ashe.
Nunu: Very underestimated because many of bad players play him. I don't know why. Give him a try. He is tricky to learn but has a large potential.
Pantheon: One of the coolest melee DPS. If you have the skill, he is very powerfull. Need the skills though.
Poppy: Just call her OPPY (OP). Ult someone with no damage and tower dive the rest of his team. You have 6 seconds. It is usually enough to kill 2 or 3 of the opposite team.
Rammus: Good Rammus are hard to find. But when you have one, he is better then 3 Guardian Angels. Give him a try.
Ryze: Spam your abilities.
Shako: You can be a pure ****** with him. You can also make the other team nervous just because they don't know where you are. Which one are you?
Shen: If you like to Kill-Steal, pick Shen. Most of Shen use their Ult to KS you. When you need them to cover your back they talk about a 'Cooldown issue'. Very powerfull and easy to play.
Sion: Another Hulk. You need skills too.
Singed: In good hands, this Champion is nothing less then OP. But good hands for him are very rare.
Sivir: The perfect beginer Champion. Upgrade your abilities in any order. It all works. Awesome pusher though.
Soraka: A quite good champion. But anybody can play her. Just heal and give mana.
Taric: A good tank but he his hard to be very effective. Some are very good with him. Need skills.
Teemo: You can call him a Super Minion if you want. He does almost the same thing. Unless you master it. Need skills.
Tristana: HUGE potential. Learn her and your friends will love you.
Tryndamere: see Tristana.
Twisted Fate: Right-click.
Twitch: You are the paper of this game. If you are patient and use opportunities, you will be a monster. Easy to be a feeder. Need skills.
Udyr: Hit Q,W,E and R. Order doesn't matter. You master Udyr.
Veigar: A good challenge with high potential.
Warwick: JUNGLE. If you don't, you are useless. Not a late champion unless you are fed.
Zilean: Bomb and Warp.
There is my OPINION. That is what I think of all LoL champions. I already know some players of Champs I do not respect will anger at me. But I tell you what I think. I play some of Champions I think that don't need much Skills and a couple that needs. Many are formidable Champions but they just don't fit in my style of play.
By the way, English isn't my main language. So excuse if I made some mistakes.