Animal magnetism would be the main quest because its associated with range., avas accumulator gives you range bonus, keeps arrows/bolts so u can use 2 rune arrows as 3-6 rune arrows. DO NOT DO IT IF YOU DONT WANT TO GAIN PRAYER LEVELS.
btw, i wouldnt bother doing horror from the deep, because these books dont really give good bonuses, they are good for obby maulers due to their low attack level, its just a little bonus, at high range level it wont really matter, you can use it to boost your prayer.
thats just my opinion, but if u like questing much then u can do some research on it, there isnt much to quest with pure ranger, thats the good point imo, when i had my pure range pre eoc, i had animal magnetism done, with low pray, like 13-27 (cant rememb) and i pretty much owned with it.