For starter mags, and for the case of Hunters and Rangers, generally you want to use a mag with high POW and some DEX; at least 145~150 POW or even up to 170 or so, and the rest in DEX. For Forces, you'll want to start off with a mag with full MIND, although in order to keep DEF low, usually you'll be forced to put some (14~17 or so) levels in DEX as well. Eventually Force classes can also use a POW/DEX mag to use melee/ranged weapon or even hybrid setups with a POW/DEX/MIND mag, but only when the Force have enough levels. It's up to you if you want to get rare mags (4th evolution); they have better mag triggers, but the stat spread is slightly less optimal as they prevent any mag stat to go above 150 (145 in certain cases).
Please note that this is for starter mags, which you'll use until your level is very high, at which point you should transit into dedicated mags which
max your stats.
Let me explain why high POW and medium DEX mag builds are the best or Hunters and Rangers. Those classes attack off their ATP stats and use their ATA stat to determine whether you'll hit. For them, MIND is not as useful (it can be useful for RAmarl and HUnewearl to equip Clio but that's very late game) and completely useless if you're playing android classes. As for why there are more emphasis on POW, it's because DEX growth via mag stat is rather inefficient, as each level only adds 0.5 ATA while POW adds 2 ATP. Meanwhile, Heavenly/Arms adds 25 ATA and Heavenly/Power adds 55 Power, which are effectively 50 and 27.5 mag levels respectively. By using Heavenly/Arms (or multiple God/Arm early on), you can buff up your stats quickly at comparatively low levels.
For Forces, early on they don't have enough stats to support both teching and meleeing, and throughout Normal to early Ultimate they're probably better off focusing on teching alone for damage. Due to this reason, the only stat beneficial to them early on is MST (MIND levels on mag).