The Mishna in Rosh Hashana (16a) lists Shavuos as one of the 4 times in the year that we are judged. The gemara in Megilla (31b) takes this very seriously. The gemara there comments that before the Yom Hadin we read the קללות. The gemara says I understand that we read the קללות in כי תבא before Rosh Hashana but what about the קללות in בחוקתי? The gemara answers that they are read before Shavuos.
On Shavuos we are judged for פירות האילן, fruits. The gemara in Rosh Hashana (16a) comments that therefore we bring the שתי הלחם on Shavuos. The obvious question is what do the שתי הלחם have to do with פירות האילן? The שתי הלחם are made with wheat which is not a fruit. Rashi there answers the question by saying that the Gemara is going with R' Yehuda's opinion that the fruit of the עץ הדעת was a חטה (wheat). However, this just shifts the question, after all wheat has not been a fruit for over 5000 years?
R' Goldvicht explained as follows. He said that fruits and wheat represent 2 ways that Hashem can deal with a person.
Fruits grow in a way that requires very little work. You plant the tree once and you forever have fruits. There is very little work in maintenance of the tree, the fruits grow every year, and you can just pick a fruit and eat it.
Wheat (really bread) on the other hand requires a tremendous amount of work. You first have to plow, then plant, then harvest, then do all the other melachos (winnowing, threshing, sifting, grinding, etc.). You can't just pick it and eat it. The next year you have to repeat the whole process.
Fruits represent the way the world was before the חטא, even wheat was a fruit. Food was easily obtained with little or no work and therefore man would have time to fully devote himself to serving Hashem.
Wheat or bread represents the world after the חטא. We live in a world of בזעת אפך תאכל לחם. It is a very difficult process to make that essential staple of life, bread. We have to work hard just to feed ourselves.
On Shavuos we are judged on פירות האילן, meaning we are judged how is Hashem going to relate to us, is he going to relate to us like before the חטא or after the חטא. Is our food going to be easy to obtain or is it going to be difficult. This is why we specifically bring the שתי הלחם, we want to remind Hashem that wheat was once a fruit as well. We hope to return to the days of before the חטא and have our food provided to us so that we can better serve him.
Hopefully we will all be זוכה in the din on פירות האילן this Shavuos and therefore be זוכה to have פרנסה ברוח ולא בצמצום and to be able to focus our energies on עבודת hashem and not on putting bread on the table.