Low Level Build Advice:
MAX INT FIRST before you do anything else. After this if you are using a DEX build you have three options.
1) Add 135 AGI first and use Hit Xtals/Gear so you can hit stuff that you will be leveling on. You will be able to melee earlier than with other options. Your damage however will be a lot less than that of a 140+ Enchanter.
2) Add 43 DEX first. You will be leveling as an APP High Wizard with this option until 140. You will max ASPD at 140 with Swords if you do this.
3) Level using a High Wizard build and use a Stefly's Book at 140. This is the easiest option but requires a Stefly's Book which not everyone will want to get.
CRT builds are typically gonna be much more difficult at lower levels so I don't recommend it but as far as I know they are pretty simple. Get 200+ INT(preferably maxed but for CRT builds it could be better to have less INT at level 140 for CRT builds), get 135 AGI, then max CRT. Use Hit Xtals/Gear or Crit rate gear until you get high CRT.