I have installed sql server 2014 and configured an in-memory database for high performance on large tables. I want to Gain further performance by adding more servers to it if possible. What are the general guidelines having best performance and in particular can we set-up a Grid  for the same database. 

Thanks

There's no transparent functionality for scale-out, at least not for all-nodes read. Se depending on your exact requirements, there might be functionality that will help you, but we'd need to now more. There are stuff like replication, readable secondaries, do-it-yourself, distributed partitioned views, etc...