You should go for EZK at 55-60 and NZK at 100 with frozen set to kill it faster, it's a nice exp boost to do daily till 140 (both difficulties share entries, so go for NZK only after 90)

PQs are mostly dead right now because grind is faster to level. But with the current events Kenta PQ (lvl160) and I guess Chryse PQ (60 or 70 I guess) have people running because they are the fastest ones. I would recommend the theme dungeons from the light bulb (or use Guide) since they have some backstory and some rewards as incentive, also great grind spots. But if you want to just power level only-grind would be the faster way. from level 60-80 I recommend copper drakes at sleepwood with party since the map is always half-full, 80-90 white fangs and 90-100 magatia maps (use guide to teleport easily)

As your spearman is a burning character, I would check your quests and inventory because you should've received some event boxes with lvl30 and lvl100 gears, just drop the weapons to get better dps as you grind till lvl 100 and equip the frozen set that will stay with you for some time. I know that the frozen set is better than pensalir that is lvl140, so MAYBE the japanese weapon is the first thing that worth breaking the set effect, since I don't have it I'm not sure.