Gaining armor points is not as straight forward as you might think it is. There are 3 key factors in determining the rate at which this XP is gained.

1) Game will generally extend the viable gained XP to +/- 4 levels differential bethween you and the enemy. 5 is a strech and should only be bothered in a dire case, since the gain from that much gap is mindblowingly puny.

2) The less resistance and armor value you have on your plates, the more you'll get soaked by damage, and therefore the bigger the gain in XP. For this particular purpose of grind, your defenses should be balanced bethween having enough armor value to create buffer to prevent you getting nuked, and still be small enough to get good gains. In this extent that starter set you get after Allowance is plenty.

3) Each mob can only provide a fixed amount Armor XP. Do NOT forget this!


And to get started, head to Digger Cave. Why this location exactly? Because individual Acid Diggers are weak and deal very little damage, so even a group of them will not suffice a serious threat. The entrance has an ammobox to keep you in there, very nice.

The rest boils down to mob- and health management. Your Armor/Weapon Point cap is determined by your character level, it is important to keep that current cap in mind and check your gained points often.

You'll want aggro a decent group, 3-6 is very fine, and let them deal their damage. Keep an eye out for your HP and track the gained points often. When you notice you've hit the gainable cap from these mobs, wipe them.

You'll aggro another group, and repeat the process. But this is where point management comes in. You will always want to maximize your gained points in contrast to your character level. Spend them to whatever Type Masteries you can at that point, and if not sufficent for anything, it's a fine chance to get some of those Armor Inventory Slots opened.

From this point on, it's just rince and repeat. If you happen to die, at least the distance to get back is quick and short.

We do it this way to keep your character level skyrocketing, which in turn may cause problems later in the game with Weapon XP gains. Think of this kind of management as a failsafe for future progression.

This video is a demonstration of the process.

BE ADVISED!
It is long, boring, bad quality and will make you blow your mind out of boredom, but do enjoy it if you think it helps.