In Tableau - use "Live" Connection, in case you have a big data platform that supports fast analytics like Google Big Query, or Cooladata.com, that also automatically manages the DWH, and the ETL process to it, with Behavioral analytics enrichment.
So in the end you will only need to worry about querying your data in Tableau.
You can also try to use the "extract" option. but that might require a lot of RAM.
Have you done a performance recording to see where the bottleneck exists? Honestly, 4GB of memory is too low especially if you are working with a lot of data and doing anything else on your machine. I typically have Tableau, Chrome, Outlook and a chat program open and I am already using 8 of my 16GB of memory. The performance recording can tell you if there happens to be any issues with your data connection, but I suspect it is your actual machine that is having difficulty.