Introduction
I'm sure you know what blades are, so I'll skip the introduction.
Skill Descriptions (mercenary)
Slash/Keenwheel-Slash hits twice pretty quickly, while keenwheel hits three times. Pretty good for high STR builds, especially against high block classes like bow jesters. (Remember that this is strength-based, while all blade skills except for Cross Slash, which I hear is pretty much useless.)
Sword/Axe Mastery: +100 damage with the specified weapon when maxed. Very good.
Blazing Sword: +50 damage and 10% hit rate using swords when mastered. Definitely max it if you're a sword user.
Smite Axe: Not totally sure about the exact bonus when mastered, but I'm almost totally sure it's +50 damage and defense. Might be +20 defense, though. Either way, definitely max it if you're using axes.
Builds before you become a blade (Mercenary)
I personally use the following build from level 15-60. (should work pretty well with swords or axes, but I personally use swords)
Level 15
Str - 20
Sta - 15
Dex - 38
Level 20
Str - 25
Sta - 20
Dex - 38
Level 25
Str - 25
Sta - 20
Dex - 48
Level 30
Str - 30
Sta - 25
Dex - 48
Level 35
Str - 35
Sta - 25
Dex - 53
Level 40
Str - 40
Sta - 30
Dex - 53
Level 45
Str - 50
Sta - 30
Dex - 53
Level 50
Str - 55
Sta - 35
Dex - 53
Level 55
Str - 55
Sta - 40
Dex - 58
Level 60
Str - 57
Sta - 40
Dex - 66
It's best to modify your build instead of copying exactly from the internet, but that's the build I use. I would go into more details and builds, but since this guide is on Blades, I'll end the mercenary stuff there.
-------------
Blade builds
FULL STR
Only use this if you manage to get a +10 set. If you can get one, it's VERY good in PvE. (doesn't matter as much in private servers, though, because you won't need to PvE very fast with the rates.) If you can't get a +10 set, don't bother using it at all.
High strength (axes)
34dex
15-40sta
rest STR
Still very low DEX, so you'll probably need atleast a +8 set, although a +6 set might work. If you can obtain a +6 set, then this is very good for PvE, but as I stated in the previous build, you won't need to PvE that much in a private server. High strength builds aren't exactly built for PVP. (usually)
Average/High strength (swords or axes)
54dex
15-40sta
rest STR
Decent (decent means okay, not great, mind you) build in PvE. Atleast a +6 set is pretty good. Oh, I forgot to specifically mention this before: you don't really need the sets in this server, seeing as you can still level fast off of stuff 5-10 levels below you.
Average strength (swords)
66dex
15-40sta
rest STR
Most people would know this, but there's set DEX levels for classes to raise attack speed, such as 66 and 54. Anyways, this is the build I personally start out with as a mercenary. (40 stamina/66dex/57str) IMO a pretty good build.
DEX build (swords)
96dex
15-40dex
rest STR
This is a very, very inexpensive build, although its killing speed is much,much lower compared to other builds. I would definitely not use it in a private server for PvE.
AoE Build
80-100sta
rest DEX
Blade AoE uses DEX for its power. And since this raises block rate, the player can take a good bit of attacks. Not really much else to say here.
PVP build
DEX 100
STA 60
rest STR
This is a build I use for PvP. It's pretty good IMO. (except against crucio psykeepers, of course. blades can pretty much never beat them.) It provides a decent amount of HP,and a very high block rate.
----------------------------
That's about it for now. I'll add blade skills later.