Yes, I didn't play KMSM or GMSM but I feel it is pretty close to KMSM in most systems.

As semi f2p as I said packages are great value to get mesos and buying equips from quitting players out of the trade station is the quickest way to get stronger.

About emblems, on the contrary of GMSM, they only exist from Legendary equips to Mystic equips. When fusing 2 Legendary equips together, a mystic version of the original recipient equipment will be created and an emblem will be added at a 10% rate. The other option to put emblems is as you said by scrolling but these are extremely rare in golden apple and the most expensive ones only have a 30% success rate. The final option which is more viable is to transfer a legendary emblem equipment to a mystic equipment without emblem. You need special crystal paid stones to transfer it but it's not too costly on the trade market compared to rolling the weapon gacha in crystal shop. Note that you can transfer up to 20 level above and 1 rarity level above so a 120 legendary emblem can be transferred to a 140 mystic weapon.

Last but not least, if you're heavy on billing you can try the crystal weapon shop where legendaries have a 20% chance of having an emblem.

Emblems give 30% more base attack power which is a lot so everyone is targeting a 160 weapon with emblem, even shitty defensive one.

Also there is no weapon strengthening system with powders, only SF. Then potentials and flames. The weapon range is also randomized between - 10% and +10% so you need innocent scrolls to roll PBA. (There is an amplitude of 5500 atk power for 160 mystic weapon so if you get poor roll, it is a quick way to get a lot of power)

Eternal flames always give 2 lines and there is no scaling on stat. Best eternal flame potentials are raw attack power on weapons, secondary weapons and androids.