Bismihi ta'ala
Khums is a wajib duty applied to every mukallaf. Once you reach the age of taklif, you are independently responsible for your wajibaat. If you meet the requirements of khums, then you must pay it, regardless of whether you are financially dependent on someone else or not.
As for gifts, you will need to refer to your Marja' taqleed, to see if according to him, khums is applicable on gifts. According to A.U. Sistani, it is.
So, if your khums day comes, and you have yet to use that gift, or you have savings, then you need to pay its khums.
And Allah knows best.