Veil levels are useful for a lot of cases, and Moonlight levels should be based on them. See the spoiler above for full details, but for practical purposes, 30 Veil and 20 Moonlight are probably the most we should go for. 15 moonlight and veil up to 25 is more than likely enough.
Remember that it's best to take moonlight levels first due to the training process.
Eclipse scales fairly high in theory, because it gets good special abilities with levels and has fairly low base damage, but it's a pretty low priority except for reflected godlight purposes. Especially because we can use our weapons nonlethally.
Become whole again needs no more leveling, no matter how curious I am what it gets at level 40 or 50.
Supernova, as an AoE spell, scales near-indefinitely due to it's vast scale and potential usage against DBs. Level 40 is notable.
Scorching Sunlight is unlikely to require more than level 15 against anything it can target, but levels remain useful up to level 16-17, where a single cast deals over a million damage. Due to milestones, may be leveled to 20, where a single cast deals over 21 million damage. (Synched casts deal 80 to 125 million.)
Flight is their only non-exponential ability, but is needed against fast people. Level 20ish on moon should be enough to deal with most, especially if sun gets speed gap. That's really expensive, though, so it's basically an emergency purchase. Even then, casting Supernova should catch most fast opponents, especially at higher levels.
Event Horizon and reflected godlight are expensive mystery boxes with extensive prereqs. They should be both useful and interesting.
Speed gap is nice, but specialized. One of those "Buy if we Need it" items, though the req is annoying.
Same for Overtake Greater.
Solar seal is mostly irrelevant due to Mistress of the Tide.
Raging Shine is fairly meh. We get enough Moon damage with scepter levels, and they also give APT and abilities. It
could be great, but it's a gamble, and we're fine without it.
Moon's omnicaster is useful, of course.
Julia is a plot-based purchase. We have the spare XP to do it if we want. It will almost certainly make up it's price, even now.
Celestial ascendance is...ahahahahahahaha. No. We aren't getting that much XP unless I'm horrifically off. No matter how much I want it...
World Eater...no need to spend on her defenses due to Mistress of the Tide. Her spells are lethal enough already. Her weapon could have levels, but even then, spending on sun's scepter generally helps more due to Radiant Shine. Spending for advanced life sense is a decent choice, as is complete connection (though that's a plot-based purchase). The other abilities haven't prompted much interest. Healing, a probable save from death, and grand devourer, which does...something related to eating people?
