You may be able to swap out your current cassette for one with a larger cog count in the back... I changed mine from a 11-26 to a 12-32 for instance, that was the max I could put on it with the current derailleur. And yes, it helped quite a bit!

Depending on your drivetrain, you may not be able to put on an 11sp cassette if you don't already have an 11sp cassette, if that makes sense. How many cogs do you currently have? I don't know much about mixing different speeds on the same drivetrain, other than 8 and 10 definitely don't mix (had to replace some parts on a bike I picked up that had a mix match, and it wasn't shifting good...)