Oh I missed the recycle shop
The 1st option is to buy stuff from recycle shop
which contained:
jackpot? silver chest - 29 exchange coins
dungeon reset - 85 exchange coins
superior gem abrasive - 235 exchange coins
stats reset - 990 exchange coins
superior warrior necklace (7 days) (str+20, dex+20, con+20, magic def+85) - 65 exchange coins
superior magician necklace (7 days) (pdef+85, int+20, con+20, spr+20) - 65 exchange coins
superior health bracelet (7 days) (con+45) - 45 exchange coins
superior psychic? bracelet (7 days) (spr+90) - 45 exchange coins
5kg dumbell - 250 exchange coins
shovel - 250 exchange coins
bubble wrap - 250 exchange coins
detector - 250 exchange coins
2nd option - exchange your hat obtained from the gacha to get these exchange coins