One Dataset multiple reports

Hi 

Quite new to PBI so still finding my feet. I like the idea of having multiple reports in a workspace that can be emebeded into a dashboard but im not sure what best practises is on creating datasets. 

For example, say you have a page with 3 bar charts (Orders by Style, Orders by Month & Orders by Color) connected to the same data set of individual order records. I like the way you can create these off the one data set and then they all adjust when you select items with each. But say I also want to show a line chart showing year on year orders for comparision should i create another dataset that has been already aggrigated and just ready to diaplay or is it more recomended to some how aggrigate the current dataset so that you are only doing one trip to the database. Currently as my knowledge of PBI and DAX is not great i find myself tending to create many datasets to do slightly different things.

Thanks.