I did the Master +1 for the new event earlier today, and got the materials to upgrade Heathcliff to 5*. And man, 5* Heathcliff is a giant upgrade over the 4* version, I'm honestly (and pleasantly) surprised they made him that good. His stats got a nice bump ( I was only keeping track of Attack, and it went up by about 300 points). His battle skills got changed to match the Gatcha 5* (4* had 1 skill to up attack, and one for MP, 5* had a combined version that gives 15% each, and Leader skill +6% attack). He also now gives combi skill with Asuna. His SS3 may also do more damage, but I don't have a baseline for testing.
Now I'm really tempted to upgrade my Start Dash Chars. People on reddit have already been saying how it helped cut down their timing on the ranking event, so it probably boosted that stats or their SS3 damage. And even though their bonus is only 5% on combi skill, its a much easier requirement to fulfill since its just same element (and for ranking events you want to use the whatever the boss is weak to anyway, so you'll be boosting your best elemental char)
How often does the stardust store refresh? I already got my rainbow essences and another 1000 medium stardust so i wonder how safe it is to spend anything above that for medallions.
edit: What should be my strategy for MC spending
I currently managed to get:
5x 5* units (3 gatcha+ event Kirito , Eugeo)
8x 4* units (6 gatcha + Black Wing Kirito+ Idol Yuna)
4x 3* healer
On the weapons front however all I have is 2x 4* gatcha weapon and bunch of 3* - plus gazillion of 4* golden/blue swords from current events so I'm doing not so great.
But the last time I tried doing weapon gatcha all I got was 2x3* weapon so I'm kinda afraid of blowing diamonds for nothing.
So I wonder if I should try to get mds fast and try again on weapon banner in hope of getting something dedicated to my units but with real risk of getting crap. Or take more of long term approach and just collect mds until I have enough to reach another step 5 on characters banners in the future and hope for weapon banners with another guaranteed 4* pull in the future.
On Stardust, it varies. theres no real fixed timing as to when the shop refills. Its not just rainbow essence but medallions can also run out (esp void). The shop has been out for a few months but there were only like 400 medallions per type for a long while, it only got bumped to 700 recently, and that was in one shot.
On MD spending, I don't know exactly who you have and what weapons. The old consensus was get 3 4* character (for a full team, 6 for double rankings like this), then go for weapons to equip them. Along the way, try to fill in missing elements so you cover all of them with 4*.
Guaranteed weapon pulls (heck any guranteed pull) are pretty rare. This is only the second one, first was when OS was released, so I wouldn't count on another one arriving anytime soon. The Step 5 guaranteed 5* was also new to the anniversary, so no one knows if its a one time thing or typical going forward.
But yeah, I think you are pretty set on the character front with 3 gatcha 5*. You should probably prioritise weapons a bit more, at least till you get them equipped.
Not sure if your 5* are all from the same banner, if they are, I would multipull that weapon banner till it expires. Once the matching banner expires though, I probably wouldn't pull weapons anymore. Start saving up MD. Probably stockpile enough (like 400 diamonds) for guaranteed banners if they appear again, and if some banner comes along that fills a hole in your team (stunner, debuffer, elemental), I'll roll. If I get one, I'll use the MDs to try to get that chars weapon and even if you don't get that chars weapon, maybe it'll fit someone else.
Don't forget to use the giftbox trick to save inventory space. if your inventory is full when you do a weapon pull, they all go to your box and don't expire. so keep them there till you get enough to evolve something. R3 evolved to R4 will do in a pinch, esp if they match element. Oh and the 3* healers are perfectly happy with 3* weapons (even 2* evolved to 3*). You just need your dps equipped with the good stuff, so you end fights before you make a fatal mistake.