I
"They shall make an aron, two and a half amos its length, one and a half amos its width, and one and a half amos its height" (Shemos 25:10). The Kli Yakar explains that all the dimensions of the Aron, which represents the Torah which it housed, are fractions, containing half-amos, to teach us that everyone should understand that the breadth and depth of his wisdom is lacking (fractional, so to speak), since his intellect is limited.
A person should pray with his eyes looking down, and his heart focusing up (Yevamos 105b). Think of someone who is higher than you in Torah, and pray that Hashem grant you an understanding heart (Melachim I, 3:9). His eyes, which behold physical things, should look at someone who has less than him, and then he will be happy with his portion and not ask for excessive wealth (Mishlei 30:8).
"You shall make a shulchan, two amos its length, an amah its width, and one and a half amos its height" (25:23). One should say, like Yaakov Avinu, "I have everything" (Bereishis 33:11). The whole numbers indicate that in worldly matters, represented by the shulchan, the wise man who is happy with his portion is not missing anything. The fraction teaches that he should not indulge in physical desires totally, but rather he should break his desires. Eating bread is, therefore, called breaking bread (Bereishis 43:2), consuming only a fraction of the whole.
"You shall make a mizbe'ach, five amos long, five amos wide, and three amos height" (27:1). By atoning for a person's sins the mizbe'ach completes that which his deeds are missing, and therefore all its dimensions are whole numbers.
II
The Kli Yakar's idea of looking up spiritually and down physically was echoed by the Ba'al Shem Tov. His Chasidic interpretation of "On the heaven above and on the earth below" (Devarim 4:39) requires that we compare ourselves to those higher than us spiritually and try to emulate them. Regarding earthly matters we should compare ourselves to those who have less than us, and thereby be happy with our portion.
Unfortunately, too many do exactly the opposite. They rationalize their level of Torah learning and observance by pointing to others who are on a lower level, while in worldly pursuits they look up to those who have more. They seek and pray for excessive wealth and display it even if they don't have it (See Kli Yakar on Devarim 2:3). This ostentation creates harmful jealousy in our communities and beyond, leading to disastrous results (ibid). By contrast, the "jealousy of scholars increases wisdom" (Bava Basra 21a) phenomenon, represented by the fractional dimensions of the aron, is missing.
The parsha begins, "Speak to Benei Yisroel and they shall take to Me a portion" (25:2), which the Ibn Ezra explains to mean that one should take from himself and give it to Me (Ibn Ezra). Just as we must break bread and leave over a fraction, so must we leave over a fraction of our wealth and give it to Hashem. We give "to Hashem" by donating to the poor or to Torah institutions. The recommended fraction of one's income to donate is one tenth or, preferably, one fifth (Shulchan Aruch Yoreh Deah 249:1).
Unfortunately, many do exactly the opposite - they spend large amounts of money on luxurious items and/or activities, yet do not give the preferred or recommended portion to tzedaka. Conspicuous consumption is doubly harmful because it creates jealousy and decreases charitable giving.
Parshas Teruma is the Torah reading which emphasizes the importance of donating to good causes and the centrality of Torah (See Shemos 38:21). As we read it, we must establish for ourselves proper priorities and aspirations and internalize these lessons of the Kli Yakar and the Ba'al Shem Tov. We should be jealous of those who are greater scholars than us and thus be motivated to increase wisdom. We should be happy with our worldly portion and compare it to those who have less, and not be jealous of those who have more. May we thereby merit the restoration of the aron, shulchan and mizbe'ach in the rebuilt Beis Hamikdash.