למען תלמד ליראה, "so that you will learn to revere, etc.⁠" When you will meet priests and Levites in Jerusalem, scholars who teach you Torah you will learn to revere the Lord.
The Talmud Taanit 9 quotes Rabbi Yochanan as saying about the words עשר תעשר that the Torah implies you should give your tithe עשר, in order that as an eventual result תתעשר, you will become wealthy (i.e. read as if the dot is on the right side of the letter ש.) Actually the wording does not contain an allusion to עושר, wealth, seeing both the letters ש have their dot on the left side, imply passivity. What Rabbi Yochanan had in mind was not עשר בשביל שתתעשר, but עשר בשביל שתעשר, "give your (first time) tithe so that you will enjoy many years when you have what to tithe.⁠" [When understanding it thus the dots on the letter ש remain on the left side. Ed.]. This then is the "wealth" Rabbi Yochanan was speaking about. (Based on Raav'ad, but never printed separately in this form.)
This is certainly something in the category of an experiment, i.e. appears to violate the commandment not to "test the Lord" (Deut. 6,16). Our sages in Taanit 9 were quite aware of this and this is why they quoted Malachi 3,10 where the prophet apparently allows this one exception to the rule not to test the Lord.

A Midrashic approach: The repetition of the words עשר תעשר are a veiled warning; if you do not give your tithes you will become impoverished rather than remain more wealthy by withholding the amount in question. The wording also contains a hint that people who travel overseas should donate 10% of their profits to the people who toil studying Torah (Tanchuma Re'ey 18). Another meaning of these words (Yalkut Shimoni 892): it is customary that when a person rents a field he has to give the owner at least a third or even half of the harvest. Seeing that we are "renting" the land from God and He provides rain clouds, dew, manure, etc., and demands only 10% of the harvest as His due we really have nothing to complain about. Considering all these facts Moses warned the people to be careful to observe this commandment meticulously. There was a farmer once who fulfilled his duty and tithed his harvest properly. As a result he was left with a net amount of 1000 measures of grain. When he was about to die he told his son to be careful to observe this commandment meticulously. He told him how much a particular field yielded annually and to be sure to give 10% of that amount to a Levite. He also told him that he himself had been able to subsist comfortably on the harvest of that field after he had set aside the tithe. The son, a miser by nature, sowed the field and in the first year it yielded the amount his father had told him about. After the first year's harvest came in the son dutifully set aside the 10%. In the second year, he was too miserly to do this and set aside only 9% instead of 10%. He found that in the third year this field yielded only 90% of the regular harvest. Becoming upset about this he again decrease the amount he set aside for the tithe until after a number of years of such miserly conduct the field yielded only the amount which his father had given away to the Levite as a tithe. When his relatives and neighbors became aware of this they all dressed in white garments and approached this farmer. When he saw them, the son of that original owner was upset that these people apparently celebrated his misfortune [wearing white is a symbol for celebrating. Ed.] The neighbors said that they certainly did not come to gloat but seeing that in the past he had been the owner and God the priest (the recipient of the tithe), now the tables had been turned and this farmer had become the priest (requiring the handout) and God had become the owner. This is what Moses meant when he warned: עשר תעשר את כל תבואת שדך, "if you do not give the tithe you will eventually have to be the recipient of a tithe (handout).⁠"

היוצא השדה, "which the field produces.⁠" Tanchuma Re'ey 18 comments that "if you merit it you will go out and sow your field. If not היוצא השדה, the one known as "going out into the field,⁠" (the Torah's description of Esau) will harass you (compare Genesis 25,29).

תבואת זרעך, "the produce of your sowing.⁠" if you merit it the reason you go out to your field will be to examine if it needs rain and if so you will pray and God will respond. If you do not merit it the reason you will go out to the field will be to bury your dead. [The whole line is based on the words היוצא השדה really meaning "he who goes out to the field,⁠" not "what comes out of the field.⁠" Ed.].

מעשר דגנך תירושך, "the tithe of your grain harvest, your grape harvest, etc.⁠" It is only "your" grain harvest, if you tithe it; if not it is "My" grain harvest. The same applies to the grape harvest and the "oil" harvest. This interpretation is based on Hoseah 2,11: "Assuredly I will take back My new grain in its time and My new wine in its season, etc.⁠"
שנה שנה, "year after year.⁠" This means that one may not tithe from one year's harvest for the following or the previous year's harvest. Each harvest has to be tithed separately.

ובכורות בקרך, "and the firstborn males of your cattle.⁠" This does not mean that the (ordinary) Israelite is allowed to consume its flesh, seeing that first born male animals may be consumed only by the priests. It means that the people designated to eat these animals are encouraged to do so.

We have to remember that such firstborn animals are perpetually sacred, i.e. even nowadays when there is no Temple and even in the Diaspora. Such animals may not be shorn, used as working beasts, and may be eaten only if they developed the kind of blemish which disqualifies them as a potential offering for the altar. This view does not correspond to that of Maimonides who wrote in Hilchot Bechorot 1,5 that the law of the sanctity of a firstborn male animal is not applicable nowadays except in the land of Israel. Raav'ad already attacked this comment of Maimonides stating that even according to the view of Rabbi Akiva who did hold this way he meant only that the firstborn male animal nowadays cannot be offered as a sacrifice. This does not mean, however, that the firstborn male animal does not have a sacred body even nowadays and even in the Diaspora and it is out of the question to permit it to be eaten unless it developed the blemish we mentioned. The proof for this view is cited from Sanhedrin 5,1 where Rabbi Chiyah said to Rav, the son of his sister that seeing his nephew decided to emigrate to Babylon whether Rav would ordain him to make rulings there? He was told that whereas he was authorized to make rulings in matters of foods which are forbidden or permitted and in judicial matters, his authority would not extend to make rulings concerning the status of such firstborn male animals. Clearly, Babylon is considered part of the Diaspora. The reason Rabbi Chiya's nephew was denied such authority was that these laws of sanctity did apply there. If not, why did the question arise? There is yet another proof that this sanctity applies even in the Diaspora from Bechorot 31.