Spearmen are the most popular character in VN version, mostly because of their huge attack dmg. Spearmen do have great dmg but low def and hp. Spearmen rely on their 1-hit skills and are great soloers at the beginning. But at high lvl (60+) they need to rely on parties (that constain healers) to be able to lvl effectively. Spearmen also have pretty slow attack speed compared to bladers and swordmen.

About Spearmen build, theres alot of conversations in VN version, no one has found the "best" build yet.
Heres some suggestions:

Max first skill [max lvl 20] - first skill raises your defence.
Max your fifth skill [max lvl 20] - Propably your best skill, Ok theres a system for all characters that when you deal certain dmg theres a bar that when its full you will get "few seconds" berserker mode, which raises your dmg and def by alot. But it doesnt last very long, when you max this skill you will get 70 sec berserker mode for spearmen.
Max your seventh skill [max lvl 20] - Im not sure of this, as I dont see the real effect cause my spearmen hasnt max this, but I heard it either raise your attack and def by 20% or raises attack and def by 20% while in berserker mode, anyway recommended to max.
Okay now many ppl have made exceptions for by adding to third skill which raises your attack speed, as some ppl see great attack dmg and great attack speed will be better than attack dmg and def.
After lvl 60, raise or max your eigth skill - raises your def by 2 per each point you add.

Maybe you can see why spearmen are so popular now, their skill dmg is great, their normal dmg is great plus they can choose great attack speed or great def.