Some advice on the upcoming Legendary Banner?

Just Luck, the first time that L! Hector show up, i spend like 430 orbs and i didnt get him.
So you can get her very fast, or very late, the amount of orbs only increase your chances but there is not guarantee.

Best to go with all color orbs or 3 if there is a really bad color group choice. Sniping for legendary heroes is hard when they share a pool with other 2 people. But the extra 2% chance is nice if you aren't picky.

I can't answer that for you, RNG can be a fickle thing. There will be a "Should You Pull" for the Legendary Banner after the trailer drops, which will give you percentages and the amount of orbs spent to give you an idea.

And if you don't have Ryoma or Robin, I suggest pulling on red and colorless as well since sniping a single unit on Legendary Banners is a bad idea. At least pull everything but green so you can at least get something.

I doubt Ophelia will be on the upcoming Legendary Banner since there are other banners that take priority. I expect her to be late December at the earliest.

The probability of getting any specific focus unit given a certain number of orbs is equal to the value shown in the "percentile" column here https://fireemblem.gamepress.gg/should-you-pull-eirika-graceful-resolve-edition
So for blues you're looking at better than 4 in 5.

The probability of getting any focus blue would be equal to the value shown in the percentile column for THREE TIMES the number of orbs you have, so over 95%.

I wouldn't be trying for a safe number. There's never a guarantee. One of the smartest players on this site went over 900 orbs for L.Ephraim on the previous banner and came out with 5 other focus blues, which is seriously one of the worst streaks I've ever heard of.

I've been wondering whether there's some number at which point we can say "and if that number of orbs won't do it, I'll let RNG have the better of me because I'm better off trying again next time." I haven't figured out how to calculate for such a number if it exists.