DO NOT BUY level 4 magatama, if anything buy lv2 magatama.
If you buy 3xlv2 magatamas It's at the same price as buying 1xlv4, but untill you have level 3 magatamas on everyone, it's just not worth it. you lose so much on merging them.

I'd honestly suggest starting with refining runes until you have all equipment at level 4 on your main at least. That initiative is going to win your some matches (or lose if you don't have it lel).

After that maybe go for moods (while it's still 2 moods scrolls a pop, when it's 10... it's probably not worth it anymore)

Although you're right when you have low level magatamas, you forget to mention that merging them costs coins. You should take that in consideration as well.

Thank you :)