If you're looking for agencies who have it down I'd recommend Ogilvy Social W+K Social and RGA. But it really depends on how you want to position your agency, you'll see they all take pretty different approaches.

https://twitter.com/SocialOgilvy
https://twitter.com/WiedenKennedy
https://twitter.com/rga

Before looking at other examples I'd recommend figuring out who exactly you aim to be or who your customers want you to be and go from there. There are hundreds of ways to do social and the only definition of right or wrong that counts comes from your clients.

Take a look out the ones I manage:

Twitter: www.twitter.com/thenextweb
Facebook: www.facebook.com/thenextweb
Pinterest: www.pinterest.com/thenextweb
Tumblr: thenextweb.tumblr.com

Let me know if you want to chat about how I maange them or if you have specific questions.

Matt
@MattNavarraUK

Neil Patel
Kissmetrics
Sean ellis
Andrew Chen

Dont remember their accounts but look for them! Their blogs are even cooler!

Also check out @SmartInsights they have an awesome following and are UK based. Their blog contains lots of useful tools and templates too.

And whilst not an agency, @mashable is a good example too.

Two, three or hundred, it really does not matter. What matters is your strategy. Today, social media requires a unique set of skills whereby brands need to fully understand the needs of their audience. This comes as no surprise as they are the one digital tool that can communicate and resolve problems for your customers without the potential need for any human interruption. Platforms such as Chatty people make integrating an AI-powered chatbot into your social media strategy easy. Create a personalized experience for your customers. Chatbots are not only a great way to automate certain everyday tasks, and if implemented properly, your chatbot will allow you to create more personalized experiences for your customers. To do this, stop linking your advertisements solely to your landing pages, and create ads that redirect your audience to a Messenger window with your chatbot. Create an efficient content marketing strategy. Content marketing has been a prominent form of marketing for a long time and this is not set to change anytime soon. High-quality SEO content coupled with all the above will help you bring in the right customers at the right time. Aside from its ability to attract an organic audience, a good content marketing strategy can be implemented for free. Create a community for your audience. "Although "followers” and the many other metrics are important, they are not the "be all and end all" to social media success. You need to show your audience that you are not just a robot. Integrate personality through humour and emotions into your posts so that your audience can relate to your brand. Social media is all about being social, and if your customers see the same types of posts time and time again, they will lose interest. Jazz up your content by using this type of media regularly. Today, people create profiles on every social media channel available with the aim of reaching as many people as possible. Unfortunately, with that mindset, you will not reach your chosen target audience. As a result, it is key you look at your buyer personas when choosing your social media channels. Establish a social media budget. Social media platforms are one of, if not the most important, forms of marketing. Allocating the right budget to your social media endeavours is crucial to your success. Not only this, leveraging that budget with the right strategy will be the most cost-effective way for you to reach your chosen target audience. Because social media is used on a much more personal level, you will also find that it is a place where you can make a much deeper connection with your customers.
To further engage your customers, run cross-channel campaigns across all your social media channels. Add an emotional component to your social media campaigns so that your audience can relate to your cause. Businesses worldwide are slowly becoming more preoccupied with gathering customers on their social media platforms rather than their websites.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath