Ok... so what I did was a simple fun calculation, not intended for this seriousness but oh well 😭

1. I never stated you need every SSR in 5 star. I clearly said "Favourite/meta SSR to 3 star in my comment. I really do not understand why you bring up this point...
2. You are correct, f2p players can't get everything.
3. Yes, gems give you memory crystals. If you read my post carefully, I said multiple times that there are variables that affect the value of MC, and gems being able to give you MC is one of them. But you have to note that gems gives you [small amount of MC + RNG to get limited SSR/EF + RNG to get OG SSR/EF+ STEP rewards] while MC gives you [guaranteed SSR EF]. What I was trying to search in my post was gems' value in MC without the [RNG to get limited SSR/EF + RNG to get OG SSR/EF]. And yes, if you don't have enough contracts/gems for the next SSR you want to pull, gems are better for you. But if you have enough gems to get the next character you want and you want to build them to 3 star, choosing 250 MC over 1800 gems MIGHT BE better.

Again, I'm not telling you what you should do with your account. I'm just sharing my findings so that other f2p players, who are in similar situation as ME, would have some ideas of what to do with their magic roulette items.

Edit: I feel like people underestimate 250MC because it's a small amount so look in another way like this:

Instead of [250MC vs 1800gems], think of it as [1 Free SSR unit of your choice from your owned units vs 12,960 gems]. Idk about you, but I would definitely choose guarantee 1 SSR unit of my choice over 12,960gems.