I will answer the queston as my old college professors would have if I had asked them: The best armor for you to buy "depends on a lot of variables." I always loved that answer "it depends"
It is difficuilt to give one definite answer for your question, although many have outlined similar armor purchase paths that have been effective for them, and you could follow with the same success.
My armor purchase path was:
Pixie > Rascal > Nem
I have added full sets of 5b and 6a plates depending on the circumstances. I don't fight enough electric, acid and cold dmg mobes to need any of those other plates that protect against them.
Please correct me if I'm wrong, but I think it would be more accurate to say, Ceteris Parabis (other things the same) the higher your evade/dodge the lower your requirement for armor.
Obviously, there are a lot of other variables and dependencies to consider here, mainly hp, the dps and type of dmg of the mob your trying to kill. But from what I understand, Evade and Dodge are the two Defensive skills that reduce the mobs ability to hit you, effectively reducing your dependency on armor (and fap).
Armor and Faps are just tools we use to extend our hp thus allowing us to stand and fight a mob that is above our av's capability for a longer period of time allowing us to get them, before they get us.
In fact, If you appropriately match up hp, mob dmg, weapons, and skills, then you can kill the mob without using armor or fap at all.
I like to do this every once in a while to see how my skills are progressing. I can see this by the steadily increasing difficulty of the mob I am killing without the use of armor and fap. This usually works until the mobs gang up on me! Then its usually a trip to the revival terminal
Side note, It always cracks me up when a player in armor fighting the same mobs see's me get killed and calls me a noob in disgust at my attempt to kill a mob with no armor! Yeah, I'm a noob, so what ???
(edit: I never leave a half dead mob in the field to harrass others if I can help it, I will put armor on and tp back to kill it if I need to)
Early on in my PE experience, I met Manic, who helped me get revenge on a Neconu provider that killed me when I was in my pixie and had considerably less skills then I have now
He was able to kill this neconu in his street clothes, and I think he took one hit from the thing that did not even phase him... This drove home the point of having high evade to me and has been my quest every since.
I also enjoy seeing how much more dps I am able to deliver based on my quest for ever more powerful weapons, but that's just another variable in the equation
If you have high enough evade/dodge, you don't need to waste money on decay of armor or fap.
With that said, I am in the market for Angel and better faps, because I am always pushing the limit of my av's ability to kill harder and harder mobs. I am not ready for shadow yet, but someday... That is how I have fun. I love the challenge of it. That's what I enjoy doing with my fun money.
Cheers, looking forward to your responses.