Readyboost is mostly worthless.
I studied it considerably when it first came out.
The premise is that a suitably fast usb device has a small access time, and a not so good transfer rate.
Ready boost will preload onto the usb drive up to 4gb of what it thinks it can fetch faster than your hard drive. This will be mostly small modules.
If you have a ssd, readyboost is pointless.
It is not a substitute for ram, which is a common misconception.
If you have a usb3.0 device, then it is worth a try.
It is easy to try. Just see if you can notice a difference. I did not.