[convector]

what do you suggest me to do ?

Get a virtualization software (VMware or VirtualBox, pick your poison), install your favorite Windows OS (make sure it can still keep up-to-date) on a virtual machine, get the any web browser, create throwaway email, sign up at infected forums, pick any RAT you like there (make sure it is the latest), get a decent crypter (latest as well), and start playing around.

About picking a RAT, it doesn't depend on us, depends on what you do and what you want to do with it. Just google the RATs you found and test it one-by-one. Lol.

You can watch YouTube videos, there are a lot. There are also open-source but I believe most open-source RATs you can find are just for show-off purposes. Get a cracked version of premium RATs the website I suggested (https://infected-zone.com).