I would full length size any cases that have been fired in a different rifle.
I would definitely invest in a case trimmer but imho do not buy the Lee Zip model.
You will need a .20 bullet comparator ( I use Hornady one),
Digital calipers,
Bullet puller (I use the Hornady cam lock), headspace comparator
Can't recommend digital scales as I am still looking for ones myself but I'm using a beam balance at present and have done for years.