Best approach to an ordering system

I am building the initial stages of an ordering system for ASP.NET web application to a SQL database on the cloud, and a WCF application to periodically check these orders being placed. Does anyone think that the best and fastest approach for this is to use Web API for both the calls. Is Signal R a later consideration? Or are there even better approaches. Please note I would like the best and fastest approach for this. Any suggestions? Thanks.