3 times the tube O.D. is rule of thumb, for minimum bend radius.. 3" clr (center line radius) for 1" and I would go with 6" clr for 1.5".. With the 6" clr, you can bend .065 without wrinkling the inside of the bend.. 180* dies are a must.
My first 1.5" was 5.5 clr and my first 1" was 3" clr. I added different sizes as needed. Two things I'm glad I got were the ram setup and Bendtech software. You may soon find you have more invested in tooling than the bender.
I have a JD2 model 4 bender and started out with 1", 1.5" and a 1.75" dies. But bake when the rollcage rules change for the heavier vehicles I picked up a 2" die. The only ones I want now are a 1.25" and I want to get a 1" & 1.5" square tubing dies. As for the radius of the bend CLR I think they are about 3 times the tubing plus a half inch. Because my 1" CLR is 3.5 I think but I know my 2" is 6.5" CLR. I alway have to go back and look at the dies for the correct CLR when planning out a project.
I have not even used my 1.5 " die but I am making a roof rack for a full size chevy truck extra cab and I finally get to make the floor of the rack with 1.5" tubing and 1" for the rails. I talk the guy out of doing the rack out of all 2" tubing like I used to make his bumpers.