The build you choose will depend heavily on the prestige class you wish to choose. If you plan to become a Knight, END in your build is almost essential. Yes, most of your defense will come from your gear but END creates an increase in the block rate. In contrast, if you will be a Gladiator, you do NOT want to add END in your build. You will not be using a shield so you won't be able to take advantage of the block rate. Ultimately it is your decision. Please read the section on stats.
End/Dex - Knight
Pro: Higher Evasion/Aim, HP/Defense/Block Rate
Con: Less over all damage potential due to the lack of Crit/ STR, Less M. Def
End/Spr - Knight
Pro: Higher Crit/ M.def. and all END additions. With this build I would recommend 1:1 End/Spr or 2:1 End/Spr. The idea behind this build can be to stop at 25 SPR as usual or continue to 50 SPR or more for the added M.Def.
Con: Less Eva/Aim/Damage
Dex/Str - Gladiator
Pro: High Eva/Aim/Dmg
Con: Less Hp/Def/Block Rate/Crit/M.Def
Dex/Spr - Knight or Gladiator
Pro: High Eva/Aim/Crit. M.Def
Con: Low Def/Hp/Block Rate/Dmg.
End/Dex/Spr - Knight
Pro: Balanced build spreading bonuses among evasion/aim, Hp/Def/Block Rate, and M.def/Crit rate.
Con: Not as focused in a single area. While balanced, it could be considered weaker than other pure or half builds. Very good beginners build.
End/Dex/Spr/Str - Knight
Pro: Again, Balanced. Includes the above comment with slightly more dmg.
Con: Less bonuses than the previous mixed build. Still a pretty good beginner's build.
Dex/Spr/Str - Gladiator
Pro: Once again, well balanced but also more of a "Damage Dealer" build or PVP because of the increased STR damage and the crit rate plus the Aim/Evasion.
Con: No HP/Block Rate bonuses.
For Knights STR is pretty much useless. You will not be dealing damage. You are going to be taking damage.
For Gladiators, END is almost entirely useless. They do not use shields so Gladiators do not use the block rate.
It is generally recommended that you do not add more than 25 SPR to a build. Please see the basic stats page for more information.