Dosing is highly individual. I wouldn't listen to a supplier or anyone else. I wouldn't listen to an anonymous internet poster. You need to do some research, that FAQ is a good place to start, follow the links.
Some people struggle at very low doses, some can start right out at 50 or 100 mg with no problem, that depends on a variety of factors.
I personally chose to start at a very low dose(12.5mg(2 drops lugols) per day and up my dose slowly, took me 3 1/2 mos to get to 50mg. That worked for me.