Could someone tell a places where it is good and properly fast to grind in dungeons at lvl 15 and further?
Thank you

I would like to know this as well. I'm 13 and can't pass the "Magatama Crafting" main quest.. don't know where to get the items it needs. This game is very confusing as I'm doing dungeons much higher than 13. :/

ill recomend cave of dreams at hell mode solo
if u have the daily bonus atleast 20 to 30% + exp boost 50%
then you will get almost 1.4 - 1.5k exp per run for every runs (4min./run)

Run byakko till your early 20's than ankon forest in kyoto till ~29. I personally ran kyoukutsu till 36 but many people prefer Gedoumaru or yakumo more. Shinodan is good for the late 30's and early 40's but it'll still take about an hour per level, granted I think there's a grind spot that some players are keeping secret from us... supposedly gaining a level in 30 mins unbuffed.