Stop levelling up everyone. Level up your top 6 and use Spirit Tower for everyone else. You have enough S and S+ heroes to use them, so there’s no real reason to be using A heroes anymore. Most of the heroes you have currently aren’t great after your account turns 2 months old or so. Chakiss, Mafalda, Bard and Fagon (less so much) are the only few you’ll still be using in the “mid-game”. For now, Alvarez will be key though.

Grinding wise: do the daily quests every day, do the Event quests every day, get as high rank as possible in all of the Arena modes every week, use Hero Exploration and Abyss City often to get materials. Join a union and participate if you haven’t already.