First of all: This is a work in progress, so expect this guide to change over time. I figured since the Dragons are new, I try something new and put up an unfinished guide.
Which of course means: Please rip it apart! The more the better! Have at it! Or whatever it is you do to half baked nonsense 
General points:
-
This is what we have: 1 fast, 1 avg and 1 slow dragon in each color and each rarity. No exceptions.
-
No mana troops! Means the speed is the speed and that´s it. So 8,10,12 tiles (for fast, average and slow) makes it super simple and especially beginner friendly. All assist skills for regular world are 12 tiles (slow). There are of course both positive and negative effects on mana in the special skills to change mana generation after firing.
-
Good synergies are hard to come by. The only real synergies are dragons with their own duplicates. Everything else is by definition either different colors or different speeds or both, which doesn´t help with synergizing. If you have heroes of higher rarity than 3 stars, there are possible synergies across rarities, but I don´t know those higher rarity dragons much, so I won´t talk about that. It´s mainly 3star for me
-
Fast (3matches) and slow (4matches) are straight forward. While avg speed is the tricky one. For people that are good at (and purposefully play for) making Dragon bombs they can synergize with fast dragons, for people that don´t like to think too much while playing, I would rather sort them in with slow dragons (4 matches). If you plan a synergy between an avg speed dragon (who fires first) and a slow one (that fires after), it gets as close to a true synergy as it gets. An example could be yellow: Solis (attack boost) and Glimmerwing (damage).
-
Special skills are rather weak when compared to stats, while stats are comparatively high (two of the stats are defensive, while only one is offensive). That means special skill damage especially, but in general damage is low, which means the game is slower and that also makes slow special skills more playable. Not like in the normal game, where slow is something for rush and PvE only, here you can play slow skills, they are not automatically excluded from PvP gameplay. But since maybe slow is easier to play the skills we must expect are also a bit weaker? We´ll see…
-
If you are new to Dragons (or play only occasionally) you may still be playing with dragons that are not maxed, and especially whose special skills are not maxed (10 skill levels for dragons!). which increases what I said in point 5. Skill damage is not exactly huge.
-
I haven´t looked into it thoroughly, but it seems to me that stats overall are extremely similar between dragons, and without LBs and Emblems etc, they are not up to us to change. So it looks like the stats are actually something we can simply ignore in this dragon world as they are a constant across the board.
-
In FTP world (at least the active part of FTP world) the main problem seems to be the low amount of free summons, which means you can simply upgrade all the dragons you get, without thinking about them too much. You will have more trainer dragons than you can use on your few available dragons. I personally bought that beginners pass and therefore had a bunch of extra dragons available to upgrade, but since I haven´t spent any more money since then, I can see that I will eventually get there as well.
-
Since we at current have few Dragons available even in the best of cases or when spending money (only 3 in each color) but we still want to be able to build at least a 3 stack in each color, we will basically be forced to upgrade duplicates. Even if all 3 dragons in a color are strong by themselves, the synergy between them suffers badly from having 3 different speeds on the same stack, so I prefer maxing duplicates.
X. More to come
Now lets have a look at the 3star dragons in a bit more detail. For now I will only use 2 categories: Good and Meh. That is because I don´t think any of them are horrible and none stand out above all others.
This also means, I find the balancing very well done this time! No extreme good or bad ones, and the skill power corresponds well to their mana speed. That in turn means, you can´t really go horribly wrong, just play with the ones you like best and see how it goes.
The dragons are sorted by color first, speed second.
As my first round of heroes got upgraded I switched from playing 2 healers in raids and 3 healers on the map, to 1 healer in raids and 2 healers on the map. So I did (and would still recommend) work on 2 healers among the first 5. I would say the best healers are Silva, Solis and Leafy, I chose the first two (as those are the ones I got early).
Red:
Rusty: Good! Hit 3 and a boost for tile damage. Decent combo and as I said tile damage may be more important than we are used to from the normal game…
Ardere: Good! Average speed snipers are a big no-no in the normal game, but here instead I say hardest hitting 3star sniper dragon.
Krio: Meh? The numbers look big, but if you think about it in% you get 40% heal and 20% attack boost + Molten shield from a slow dragon. But he is a decent starter dragon, that may get replaced later.
Green:
Leafwind: Intermediate. DD(rare skill!) and dodge on a fast sniper is a nice package deal. Makes sense to max duplicates. BUT: the damage sucks, even when the second one hits on top of the first one, a healthy target doesn´t die. But since there is no other green damage dealer, what else is one to do…
Silva: Good! The heal is small (20%), but cleanse, bonus heal and Skill Def boost make it a nice package.
Croakster: Meh! Big heal and cleanse. Nothing else. I prefer Silva as green healer and Krio as slow healer.
Blue:
Leafy: Good! The only fast healer. Straight forward.
Flumen: Good! The only dispeller.
Snowy: Good! The only slow dragon that only affects 3 targets. The effect is rather strong (stronger than the other slow damage dragons I think) for those 3 though, so the balancing still works.
Yellow:
Sting: Good! The Bane-Dragon (I know people call Krio that, too because we all got him for free), but here is the equivalent in skills. Fast yellow sniper with blind. Still good after 7 years Also there are only two 3star dragons with a 300% damage special (the other one is avg speed Ardere).
Solis: Good! Good heal and the Wu Kong effect. Absolute killer on map stages fire him and a fireball volley and things die, don´t need anything else. But even in PvP you can deal some serious damage. Not the greatest dragon to play unlevelled. Not as amazing as I initially thought, as the attack boost is actually not a huge as the raw numbers looked, but it is still a good hero if you have to hit targets above your weight class. But against weaker opponents the misses are more annoying.
Glimmerwing: Meh! The Hu Tao equivalent, don´t like him there, don´t think I´ll love him here, but at least you get the self heal… So not a horrible dragon, but not up to the competition in yellow.
Purple:
Sparky: Good! Interesting skill that needs synergizing, with the above mentioned problems. Maxing duplicates would probably be best, a stack of 3 Sparkies kills 3 enemy 3star dragons (or equivalent 4 and 5stars stuck on ascensions). At least if I was spending some money, but not enough to get all the 5stars, that´s what I would do… But if everybody starts doing that SG will change Sparky to not triggering it´s own ailments anyway, so not sure how long this will work. Besides that: also possible to get at least a semi-synergy with Vesperi, who adds 1 ailment (and should be able to fire after or together with Sparky) or even slow Kranio (3 ailments), but synergizing fast with slow does not sound very appealing.
Vesperi: Good! Damage and mana slow to all, is a good skill for avg speed. Possible synergy with either the fast or the slow purples. Could max duplicates as well.
Kranio: Meh? (not sure) I like the combo of long effects with mana slow. And DD effects (even if it is only SDD in this case) are rare. But no up front damage from a slow dragon makes me hesitate to max him.
My personal status
Roster:
3stars: maxed
red: Ardere x 2, Rusty, Krio, slowly working on third Ardere (not sure I need one, but got nothing else to do)
green: Silva, Leafwind x 2, Croakster (don´t need him, but when I have to get rid of feeders he´s the one who gets them)
blue: Snowy x 2, Leafy, Flumen
yellow: Solis, Sting x 3
purple: Vesperi, Sparky x 3
4stars: got Owlford and Sassy from buying the Dragon starter pass in the beginning, otherwise I am FTP on Dragons.
red: none
green: Shen Lin (not yet maxed, but will bring to 3-60)
blue: Sassy (3-60), Skydancer (3-60, hope to make him my second higher ascension)
yellow: Owlford (3-60)
purple: none
5stars:
purple: Noctur 3-70 (my first and so far only higher ascension of any dragon)
I have all the 3 star Dragons I could ever want, so no more need for those, give me 4stars lol. I have mostly stopped doing anything related to leveling Dragons, I get no Dragon I don´t already have anymore, so I don´t bother running the hatcheries anymore (1 still has around 100 trainers in it, but standing still) and even if I get 4 star Dragons I can´t bring them beyond 3-60 since I lack the non-farmable mats. And since I have tons of farmable mats, I stopped farming, too. So really I only go do enough farming and raids to finish each Dragon pass and I play the quests, that´s it for playing and I collect the 2 chests every day. Basically robot mode, minimum effort for completion, but nothing beyond that. Crazy that in more than a half year playing I manage to max the equivalent of ONE! 4star Dragon (in my case ascension 3 on a 5er). And I could scrape together mats to do one more (but not the one I want next), so let´s say two 4star Dragons since the beginning of the event. That isn´t slow pace anymore a glacier runs faster than that… But well keeps the interest low, so I don´t feel bad aout mostly ignoring the dragons.
Abbreviations:
DD – Defense Down
SDD – Skill Defense Down
DoT – Damage over time
HoT – Heal over time
I pulled so many duplicates and 3 star trainer dragons - I stopped. I guess I am going to start off-color feeding my two remaining unfinished dragons. Then I will just keep my training camps stocked with feeders until I pull something new, I guess!