Rashi: If he comes to make [an image] from wood, one who is experienced to distinguish between wood that lasts and wood that rots quickly, he will choose. Ha'Mesukan is experienced, like "ha'Hasken Hiskanti" (Bamidbar 22:30). Terumah is separation - choosing the wood.

Radak: Mesukan is like "Yeled Misken" (Koheles 4:13). Before it mentioned gold and silver - the rich make idols of gold and silver. The Oni chooses a good wood that will not rot - so much they trust in the idol (they fear lest it itself rot! - PF)

Malbim: The Terumah (donation) of the poor, who makes a wooden idol, is more elevated than the Ashir's donation. (a) He chooses wood, which is vegetative, which is higher than Domem. (b) He chooses a good wood that will not rot. The Ashir uses whatever gold comes to his hand. (c) Refer to 40:20:2:1.

Malbim: The Oni must find a skilled artisan to make a lasting image. (One who makes from metal need not be so skilled.)