Armour: Defensive stats are pretty much meaningless, 4 points of dfp/mst gives 1 point of damage reduction. It's nothing compared to the percent on the armour, which is pretty much a direct percentage reduction. While I appreciate that it may look crummy to have a bunch of 10* armours, in practice the only ones better than that are the Armas Line for its increased stamina, and Shijin for its awesome set bonus (with Ohryu head slot unit).
Shijin/Ohryu is the best armour & set bonus on Xbox, hands down. To get a Shijin, you need:
1 Haktora Sealed
1 Shuzak Sealed
1 Aoryu Sealed
1 Genfu Sealed
4 Dragon Scale (1000 AMP each, or available from Door to Subspace A-rank; check PSUpedia for more details).
Unseal the 4 sacred swords at the special exchange using the dragon scales, then trade for your shijin. Requires 99 dfp.
As for weapons... High percent is again usually the order of the day. The higher your level, the more ATP comes from your own stats, so weapon stats begin to be the icing on the cake, while the percent takes the front seat. Same for the PAs you use; they have a much bigger effect than your weapon's ATP stat.
Your stats will vary based on race, class and level, so it's difficult to know what stats you'll have at any given moment without looking at your attributes page yourself. Generally though, you'll probably be using much the same stuff at level 70 as you do at level 180 if you shop smart early on. Requirements on gear is to stop lv1 characters from using them, a lv20 character (the most common level for GAM missions) can likely use a hell of a lot of equipment. My Beast Wartecher used the exact same item list as a lv20 in GAM as at lv180 outside of it.
For a general idea, check http://psupedia.info/weapons
for the weapons you might want to look for... Click the weapon types you want to look into, ignore anything in blue cells, and hit the "conditional search" function when you're in your room.
Other things to think about using conditional search... you can set to look for the highest ATP weapon, then set a maximum price you're going to spend on it. In the name slot, you can enter the item name, or the manufacturer (GRM, Kubara, etc), an element (fire, dark, anything with "dark" in its name will have problems because of this, the game will look for dark elements instead), a weapon type (saber looks for all single, twin and double sabers for instance), and the like. Experiment with it, you may find some decent bargains.