If you've played any MMOs like WoW or FF14 recently, light level is quite similar to item or gear level. It's just an avg of your attack and defense levels across your character. In this case, since we have 10 slots, an increase of ten light across your gear slots will increase your avg by 1. Light level still determines your capabilities against enemies in a given combat scenario. Light level still directly determines ability damage like before but is more specific. 10 light above or below a given recommendation is about right. You must be at most 20 light (I think... Anyone confirm again?) below a requirement to participate.