Hello and welcome to Silkroad online!
I have been playing Silkroad Online, off and on for over 3 years. I have brought a character to the level cap (a pure str bow) only to be sorely disappointed on what I was told about pure Chinese builds.
The damage calculations in this game are complex and not straight forward. Much of the advice you find others giving are usually cookie cutter builds others had shared with them when they first started. When they get close to the level cap, they do not want to consider the idea that they had been led down the wrong path this whole time, and will thus often defend their build, right or wrong, to the end, when they finally quit the game out of frustration and go play something else.
My best advice to you is to go with what feels right. Review the skill trees at
http://sro.mmosite.com to get a feel of for each mastery's strength and weakness.
To simplify things, in general, for str-heavy builds, weapon plus fire, plus any third mastery is usually pretty solid, for int heavy builds, lightning plus cold are essential. Some die-hard folk insist fire is a better choice for int-heavy builds, but the passives and the damage for fire clearly favor strength builds. Read the skill descriptions yourself, and don't let anyone else, not even me, persuade you in this. I am just trying to give direction, up to you to feel your way around the room, mate.
Take the time to look at the damages listed on Chinese weapons and European weapons. Take note that European weapons do more damage. But European weapons will either do magical damage or physical damage. Chinese weapons, on the other hand do both physical and magical damage. The 2 damages added together make the Chinese weapon damages more comparable to Euro weapons. Thus Euros should always go either pure int or pure str, with little to no hybridization, and for Chinese, well, hybridization would be a better plan.
There is no such thing as 'best build'. The game is enough about rock-paper-scissors to say that each build has its strengths and weaknesses. What makes a build great are the players who play them, so you really need to find your style, and then learn how to make it 'best'.
That being said:
70:70 build is where you put in just enough stat points in both str and int to keep your physical and magical balances close together. When you first start off, you will be puting all stat points into int to bring the magical balance closer to your physical balance, from there, it will be more like 69:70, but as you go in levels, both balances will increase.
Is this the 'best' build? No, there is no such thing. It is, however, a very good build as it had been brewed up by someone I knew personally. His method for coming up with this build was done very (scientifically) methodically. It was tested for bow build, and seems very suitable for spear as well.