It sounds to me like you only have a couple of weapons that you use.
If you only have a couple of weapons, and they're fully fortified until the point where you need Twin Blood Stone Shards; then use the money to buy the other weapons.
Some of them are useful for different things, e.g. the Cleaver. Other weapons like your firearm and torch can be fortified too.
If you haven't got much spare money yet, don't worry you will have soon enough.
Either that or the total opposite extreme is true, and you've bought all of the different weaponsbought all of the different weapons, and fortified all of them; after replaying a lot of the levels over and amassing a lot of Blood Stone Shards.