I’m not going to be able to give you really detailed advice on what to look for while leveling with AAR. I can give a little feedback.
-You need energy regen. The easiest way to get that is by slotting ectoplasm in your jewelry slots. Points in iskandra’s elemental exchange will help too, and rushing to mental alacrity and maxing that will likely also make a huge difference. Components that reduce the energy cost of skills will help as well. I’m not sure which is better with AAR.
-It’s usually not recommended to invest a lot into spirit. I’m not sure if AAR builds find it useful or not, but more health and DA from physique is typically better. My instinct is that if, after building with gear and devotions for more energy regen, you still can’t sustain aether ray, then consider some investment in spirit, but not too much.
-It’s hard to know when to use nullification. First, if you get hit with a big DoT, so your health is draining rapidly, use it on yourself. Second, if you are fighting a dangerous enemy with an aura or buff on itself, use it on the enemy. A lot of enemies buff themselves, and the buffs are very powerful, but there’s no way for you to know what any of the buffs do without looking up monster data on grim tools. At any rate, use the skill frequently. It’s easy to forget about it. It will be much more helpful if you use it a lot, but sometimes use it at the wrong time, than if you never use it at all.
-What is your goal with your devotions? This is a prime place to pick up more energy regen. Bard’s harp is frequently mentioned as the best devotion power for energy, though, again, I don’t know if AAR builds usually take it. Also, usually each build has a few “must have” devotions, with a major priority being enemy resistance reduction. Here is a very long, but excellent guide on how to pick devotions: https://forums.crateentertainment.com/t/devotions-a-how-to-on-maximizing-them/49384.
-Your character on grim tools doesn’t have maxed resistances, so I can’t help much with gear, since your main goal should be to max those. Gearing priorities are probably 1) Maxed resistances, 2) Decent armor and armor absorption (basically as important as 1) 3)Energy regen 4) casting speed 5) Offensive and Defensive ability 6)Damage boosts to your main damage type (the importance of this depends on how much of these you already have, if you don’t have any at all, getting 100% fire damage will be huge. If you already have 800% fire damage, getting another 100% is great, but not nearly so important). By the time you’re getting to the end of elite, you’ll need to have all of those things to be successful. I usually don’t prioritize OA and DA in veteran, because it can really be a struggle at low to mid levels to keep resistances up, but I could be wrong about that.