Thats weird. You should get at least one for around 30 kills. I do know that level difference makes it even worse. Im not talking about spoil succeeding, but the mob actually dropping anything.
One type of Headless knight has much higher ratios to drop iron ore at least and the Wyrm a recipe. Is that what u mean?
I have never experienced a situation where the item doesnt drop at all, but then again L2 wiki isn't meant to be 100% accurate with our version.
As for what u mentioned about getting materials in store, u dont buy them. You can only get them useing silver coins. You can get silver coins ifrom killing mobs when you are VIP 3 or 4. But dont count on it, you wont get nearly enough to supply all ur crafting needs. Just save it for the rarer materials.
I have to say that spoil only becomes worth it after lvl 68+. At those lvls there are mobs that drop u 1:1 all the time. Also, when u go catacombs/necropolis at those lvls u will spoil more in 2-3 days than all the spoil u did up to that point. Dont give up on the spoiler even if it seems pointless in this stupid server