This question already has an answer here:
I'm in the process of researching hosting providers for a high traffic Facebook application.
The client has over 300,000 likes so we can expect quite a bit of traffic when posts are made about it and there are a dozen of so celebrities involved in promoting it on their end.
The app itself, in staging at the moment, is built with Codeigniter and is running a MySQL database. Only one table, of two, is expected to grow significantly through user interaction with the app.
Most of the traffic will be coming from the UK.
Overall page sizes with all assets loaded will be less than 1mb.
For other similar applications we have used a Cloud VPS with the following configuration:
Monthly Bandwidth - 1TB RAM - 2GB Storage - 75GB CPU - 2 x Xeon 2.33Ghz
Any advice would be great appreciated!