Which Champions should I buy?

Ahri

Sion

I want a champ that can kill tanks but i cabt find that can you help plz?

You should try Gnar

My personal pick is Taric. You can play him in 4 roles and build any item you want on him with success because he scales on AP, armor, health, attack speed (thus AD), and cdr. He also is pretty easy to pick up. The hardest parts of his kit are timing his ult and managing your passive.

Most people don't know anything about him so here is a quick rundown

Passive - after using an ability, get doubled attack speed, do magic damage scaling with level and bonus armor, and lower your cooldowns by 1 second with your next 2 auto attacks. The attack speed component doubles all attack speed, not just base. This means that something like Phantom Dancer will increase your attack speed by 90% and lethal tempo increases it by 160%.

Q - Aoe heal that can become massive if you build for it. This is where your passive management comes in. Taric's Q is a very unique ability with how it levels. The scalings/base dont' change at all as it levels. It stacks charges every time you use your passive and each level up increases the max charges. Each charge gives a heal of 20 +20% AP +1% max hp. I recently did a test build using Mikael's, Spirit visage, and Archangel's staff and the 5 charge heal was 920 HP. Keep in mind that this skill literally has no cooldown as long as you are auto attacking.

W - Link to a target ally (bastion buddy as Taric mains like to call it) to increase their armor and cast all skills from them as well as yourself. This allows Taric's other abilities to cover a much wider range and for him to support his bastion buddy from almost off screen.

E - AOE linear stun skill shot with a short delay. This is where most of the skill of playing Taric comes from. The delayed function makes it very easy to dodge for enemies with mobility while also making it very easy to land on enemies lacking mobility. Once you learn to consistently land his stun, Taric is very powerful.

R - AOE invulnerability that can hit your whole team. Timing this can be difficult, but it is quite possibly the biggest game changing ability in the game. Taric timing his ult correctly often decides who wins a team fight. I have had games with scores of ~20-40 and 6-0 towers in favor of the enemy team and my ult will cause us to get a 5-0 ace for a comeback victory.

Edit: I didn't realize this was necroed, but it was necroed by the OP so I guess it's fine.

Quinn

She's easy to play and fun, you can play her pretty much any role except support (though top or adc is recommended) You have to build crit though