The most common trims are (T) and (G). (T) means the armor will have a trim or border around it in a lighter color of the amour, like for addy it would be a lighter green. (G) means it will be gold color. This is for black, addy and rune trim. There's also "god trim" I guess, where the color is the color of a god (green - guthix, white - sara, red - zammy). This is only found on rune amour. There's also "god trim" (or called Blessed) dragonhide, where the dragonhide is in a different style then before and the color of the corresponding gods. There is no best one, though (G) tends to be more expensive than (T). God is the most expensive. It's purely for looks. The amour doesn't provide any extra bonuses. Blessed Dragonhide is the same as black dragonhide. Rune, addy and black armours can have trim. No it doesn't do anything for armor. You can't trim armor. These can be only obtained from treasure trails as rewards, which are P2P. If you want to buy, try World 1 Varrock or the forms.