I think I disagree with this take personally. I saw someone else say something similar, but starting with the helmet gives you 1: A fast win at the start of your project which sets a great pace for morale. But also 2: You get to display the helmet and have it watch over and encourage you as you finish your cosplay. I personally finished my helmet first and it was 100% for the best for me personally.
HOWEVER this is also a double edged sword as you will learn more as you do more armor pieces, meaning your paint and assembly techniques will be better and you'll have a better looking final result if you do the helmet last. This is only really applicable to those who are still figuring out their style for painting and such.
I think as long as you have fun and do things at your own pace you'll end up on top!
