+1 to only leave useful/desirable effects in the enchant table, and maybe separated by mantle type i.e. atk and def (or maybe not).
Right now it feels like you need to win the lottery twice. One is for the mantle not to break (which is very likely to break each attempt), second is for a useful effect.
For a gamble costing 6,000 RE - 8,000 RE (~usd30 - usd50) each attempt without considering the cost for an enchant hammer, it feels like the chance is very very slim.
Either make it so that any successful attempt will get a useful & desirable effect from a filtered list, increase success chance, or reduce chance for mantle from breaking (attempt can still be unsuccessful but mantle is not broken).