There is 4-5 lightsaber crystals that a knight level character can buy at creation (more if you're using multiple tracks, like Duty and Morality at the saame time, but I'll ignore those for now)
Other than the Training Emitter, the cheapest is the Loridan Gemstone. This one is so cheap, you can build a Taipani Lightfoil with a Shoto Hilt, Superior hilt personalization, and this crystal, as a brand new knight with 50 morality and +2500 credits, without any mods, for 6 damage, Defensive, Accurate, reach, Sunder and with an automaic advantage. (trade accuate for +2 damage if you go for a normal hilt instead of a shoto)
The Ilum crystal is next cheapest... and really is kinda weak. Even compared to the Loridan, it has less base damage and lacks the Defensive attribute, not to mention is also rarity 10. It's sole claim to fame is the ability to stack an improbable number of mods on it to bring it up to EoE lightsaber stats.
Next is the Mephite Crystal, at 10,000c- you need a 50 morality with a credit option to get a hilt to go with one of these. In return you get 8 base damage and the option to mod it to 11 (damage, not an allusion), and can always be found by the Sence power... for good or ill.
Last is the Dantari Crystal- if you get the +2500c option with your morality, you can just barely grab a basic or shoto hilt to go with it, if you dont mind eating ramen for the next few months. Another 7 base damage gem, it restores strain when rolling the force die in combat, as if each pip could be spent as 2 advantage. Combos well with move/hurl and the Enhance tree.
My question is, why is the Illum Crystal so weak? it has literally nothing going for it.