פרשת תרומה - Oil and Spice and everything nice

Last year, I posed the following question and received back a number of suggestions which I would like to share. Additionally, if anyone has any new suggestions, please send them or, even better, post them on the blog:

At the beginning of the parsha Moshe is told to collect numerous different materials for the purpose of building the Mishkan. He is told to collect gold, silver, copper and various other materials without any indication as to what they will be used for. Then he is told to collect oil for lighting, spices for the anointing oil and the Ketores and stones for the Eifod and Choshen. Why is the specific purpose listed for these materials but not for the others?

1. The relative value of the metals and fabrics was known to be greater and thus their importance was easily understood. It was more difficult for the people to understand the importance of the oil and the spices. They therefore needed to be informed right away of the important tasks for which these items were needed. (This answer would not suffice for the stones, however.)
   
2. This week's parsha deals at length with the construction of the Mishkon using the wood, the metals, and the skins. The oil, spices and stones are not dealt with more thoroughly until the next parsha. Since their purpose isn't discussed until later, it is mentioned briefly at the outset.
   
3. The other materials were more readily available to B'nei Yisroel. The oil, spices and stones took greater toil to seek out. As in answer 1, they needed to be informed of the special purpose they would serve in order to motivate them to find the materials and bring them in.

Please comment on the above answers or offer your own.

שבת שלום
!משנכנס אדר מרבים בשמחה