In my opinion, the most important are orange (difficult to level because there aren't many low level checks compared to other lights) and green (without those 2, you miss a huge amount of content). Also brown if you want to transform people of course ( but it's really easy to level, most checks are low level). Then purple is just behind maybe equal. Then I'd say blue, pink and red. Yellow being last.
1) Green, orange, purple (if you want slaves), brown (if you want to transform characters)
2) blue, pink, red
3) yellow
Again, this is just my opinion, Id love to hear everyone else's !
Usually, I try to focus on 3 different lights and/or 3 different characters.
I think you are mostly right in the order of lights there are some mild changes (I would put pink in tier 3 for example)
Purple (needed for slaves) is the most important light to have at level 5 by Friday because you get 2 free slaves and 40 free light exp (no energy required) if you do have it by then
Green: needed for property and for blackmail material on Ward as well as video evidence on Ms. Hill, Lydia, and Jill. you should aim to have this at level five by the second Saturday.
Orange: this is my favorite light because it is the one that gives people a fetish without totally altering their personality you should aim to have this up to level 5 by at most the second Tuesday so you can put Jane and Monica in dream chokers
Brown: this light turns people in to bimbos and should be at level 5 by the second Tuesday if you want to permanently change Jake to Jane, its also needed to youngify people most importantly Sally if you plan on meeting her during the hunt.
Red/Yellow: you need at least one of these two lights to be at level five to win the Titus fight
Blue: the only permanent thing about this light is the pregnancy, I dont see much use for it right now
Pink: has no permanent effect to it yet (and honestly im waiting for one) also you can cast dancing light on Professor Ward on the second Sunday and you will still get most of the effect out of it without being at level 5. I consider Pink to be the least useful light right now, but that can change when/if g28 adds some permanent Pink lights (I dont know if he actually plans on doing this) to the game (honestly I dont know exactly how permanent pink would work but I am imagining just having the other characters be in permanent lust for you that they are essentially cock whipped and cant orgasm unless they are either with you or thinking about you and you can then have them do favors for you in exchange for the chance at having sex with you).