Which Language(s) for my Project?

I'm currently looking at developing a Web App which will focus mainly on using API's to give statistics to the users. They will input searches etc and then the API calls will return the results.

I currently have "mild" knowledge in many differing languages e.g. jQuery, HTML, CSS, C#, XML, XSLT, ASP.NET, SQL etc however I would like to use this personal project to really focus on a specific language(s). I have lots of different ideas for websites revolving around a few different APIs, so learning a good language for this type of development would be great.

I have read lots of conflicting guides etc which all suggest different languages such as:

NodeJS PHP jQuery (AJAX?) Python Ruby and more!

Could anyone suggest a language or combination of languages which would best suite my needs?

Happy to answer any questions to narrow down on the options.

Thanks!!!