Hello!
I need to play around with IMEI numbers (that is, changing them) on several mobile phones. It's legal in my country AFAIK, so no worries for that 
The point is, I'm an absolute rookie on this things, as in: I never did anything of the sort.
Apparently the first thing I need to do is rooting the phone, then get the right software to change the IMEI.
Reassured by the plenty resources found online, I just went to the first shop and bought a brand new Cubot J5 and a second hand Samsung SM-G532F - Galaxy Grand Prime Plus.
Then I spent 2 days trying to root each one of the devices to no avail. I swear, that was 2 days straight.
Maybe I'm not skilled enough, maybe I'm just stupid.
The result is that I didn't even manage to brick my phones (given the NO CHANGES that I got, even bricking would have been considered some knd of first step towards my goal). But no, nothing.
So I decided to post for your help, and ask the question in the subject: I need to buy more than one device, so budget is of utmost importance.
What is the easiest device to root in 2020, that I can buy on a budget, with enough resources to get to my ultimate goal i.e. easy and repetitive IMEI changing?
Thanks for your support!!