Well it is possible to leave out bicheon skills, even though I wouldn't recommend leaving them all out. I have a lv 33 pure INT spear myself, and so far I only got a few skills on lv 1 from heuksal. The rest is nearly all nuke + lion shout and sometimes ghost spear petal, all combined with max imbue ofcourse.
For s/s it could be nice to get the knockdowns and stabs, as well as the level 73 chain, (but thats for later on in the game). And ofocurse the shield passive.
It can come in handy to cause some stat effects to your opponents, as well as KDing them. This will give you more time to repot your HP while dealing damage in both pvp and pve. For most bicheon skills you will do fine with level 1 books mostly, but you could max out the knockdowns (and you have to to get the last books) to get the best effect.
Hybrids would do well to max out the weapon skills too, since they deal a noticable amount of physical damage too. But that doesn't really apply to you (pure INT).
But if you get the chance, it never hurts to max out the bicheon skill books anyway. Every bit helps dealing extra damage
For now I suggest focusing on your nukes, imbue, lion shout, passives and snowshield.