Which legendaries (and non-legendaries) are worth Rare Candy?

legendaries are limited time but you will always be able to get more rare candy so i don't really think there is a bad choice on what to spend on (though obviously wait till that boss ends before using candy incase you get something better). i personally level the best of each legendary i've caught to 30 unless it was completely useless (suicuine) or terrible iv's and you have something else to fill it's role (in your case kyogre, though even a poor one should beat gyarados).

you can afford to drop a lot of candy on anything IMO and keep 100ish in reserve for when you get a mew2. as awesome as metagross looks it doesn't seem to be much use so personally i'm holding out for a really good beldum before evolving. best legends by far are kyogre and groudon followed by raikou, i'd not take any others past 30 unless fire or ice becomes useful in raids.

Worth maxing multiples if possible, or 1 max and multiple L30: Kyogre, Groudon, Raikou, Rayquaza

Worth maxing 1: Entei, Lugia

Worth maxing 1, optional: Moltres, Zapdos, Latios, Ho-Oh, Articuno

Not worth a single rare candy: Suicune, Latias

Only 2 legendaries I don't have over 30: Ho-oh at 3050 and Suicune at 1598. I have 2 Lugias over 30--3300 and 3124. 2 Raikou, 1 maxed and a 2899. 2 Moltres 2866 and 2799. 4 Mewtwo--1 Maxed and 3 others at 30. Entei at 3054. Kyogre at 3964. Zapdos 3005. Articuno at 2500. I did a lot of these legendary raids, want them to be worth using. Groudon at 3554, when I finish Kyogre then RC will go there. Rayquaza at 3397, but probably get it over 3400 and stop.

Everyone will play the way they want, but I can assure you that a powered up level 30 Kyogre, even with poor legendary IVs, will be stronger than any Gyarados. From my dex - 93% Kyogre, level 30, CP 3466; a gyarados with comparable stats at level 30 will have a CP of 2791, and at level 40, 3257. That's a lot of dust to still fall short of Kyogre.

It's still good to have Gyarados - they kick butt against Earthquake Groudon, with the double resistance to ground, but they don't have the same beef that Kyogre packs.

All that said, I think you'd be foolish to use Rare Candy for Metagross. Just walk a Beldum for a few months, and you'll have a decent amount. Or wait a bit - I bet Metagross and Gardevoir, or one of their earlier stages, will appear in gyms eventually.

And for Machamp raids, I find that my Ho-Oh is a slightly better Lugia. Sure, doesn't double resist fight, but Ho-Oh does resist steel, and 2/3 of the Machamp raids one does will have a steel attack in them, on average (as well as 1/6 having two). Ho-Oh is the safer bet, resisting everything Machamp throws at me. With a good Espeon, and two Mewtwos (C/P and PC/SB), I only get to the fifth member of the team (Dragonite) when Machamp is weather boosted and doesn't have Close Combat. Love my Machamp Ho-Oh, can't see a reason to power up a Lugia for that. Maybe Dragon Tail/Sky Attack as a Gym Sweeper, but is that worth it?

You'll get a Mewtwo someday. It will likely eventually be a special quest, specifically for the people in big cities that are competing with thousands for EX passes, just like the Field Research specials are for people in rural areas who can't get a critical mass to raid the legendaries. Niantic is responding to the needs of it's gamers, just not as fast as some of you would like.

I too missed out on the birds, as well as Raikou. Just got some Lugias in the last wave, and am looking forward to getting Moltres, and the others. Did get a really bad Zapdos (10/12/10 ads, Thunder), and haven't powered it up for lack of candy and CTMs. Both of those problems are now gone, but I think it's likely I'll get a better one eventually.

Bottom line, we don't know what the game will give us next, or how it will change. Suppose you finish your plan, using a few hundred rare candy for Metagross, and then they announce that Beldum will be the next community day special. That would kind of suck for you, and be awesome for the rest of us, as well as getting maybe a 2 bar steel charged move that kicks some butt. So, given that we're acting on incomplete information, save some resources for a rainy day, and don't go to extraordinary means (like using rare candy on non-legendary pokemon) unless absolutely necessary.

Seriously, did anyone predict that we'd see Mew as a special quest, and possibly other Legendaries as field research bonuses? Maybe a few people thought the former once data miners found the quest bits in the code (I know I did), but the latter, not even close. And we don't know what's next.

To 30:

1) Kyogre, TM to water moves
2) Rayquaza, Dragon moves

Rest as you want to fill. But I always keep 100+ Rare candy for the next great catch.

PS. NO RARE ON NON_LEGENDARY! You'll get them eventually anyway, Metagross surely will come as raid boss. It also hatches Beldum from 10 km eggs, lots of candy there!

I used a bit of rare candy to evolve my first Gardevoir and my first Metagross because I needed to make space in my bag. I don't think it was worth it, there are so many legendaries worth powering up that are just so much better than non-legendaries of the respective types. Kyogre is among the top ones, a 10/10/10 Kyogre is easily worth powering up if it's your only one. At 40 it's equal to something like a 34/50/2 IV Gyarados.

As far as needing Metagrosses with both movesets, I strongly disagree. Double psychic moveset has the tiniest niche of tanking against steel moves Machamp and if you need a Machamp tank, you should go for Lugia. Double steel is nice for attacking fairy types in gyms, but that's all it is, nice. You can just substitute with fire-types, which will also resist fairy and hit almost as hard even with dealing neutral. Metagross is a trophy and a luxury, not a necessity. I would not worry about getting one nor would I ever advocate spending rare candy on it.

Absolutely no rare candy for Metagross. It has zero use with its current moves, and Niantic will eventually give you some easy way to get more Beldum candy.