Should it be given to the priest or should it be spent as one pleases?
The writer of Deuteronomy thinks one should use it as they please (Deut 14:22-26)
22 “You shall tithe all the yield of your seed that comes from the field year by year. 23 And before the Lord your God, in the place that he will choose, to make his name dwell there, you shall eat the tithe of your grain, of your wine, and of your oil, and the firstborn of your herd and flock, that you may learn to fear the Lord your God always. 24 And if the way is too long for you, so that you are not able to carry the tithe, when the Lord your God blesses you, because the place is too far from you, which the Lord your God chooses, to set his name there, 25 then you shall turn it into money and bind up the money in your hand and go to the place that the Lord your God chooses 26 and spend the money for whatever you desire—oxen or sheep or wine or strong drink, whatever your appetite craves. And you shall eat there before the Lord your God and rejoice, you and your household.
or should you give it to the priest, as the priest has ordained it (Numbers 18:25-28)
25 And the Lord spoke to Moses, saying, 26 “Moreover, you shall speak and say to the Levites, ‘When you take from the people of Israel the tithe that I have given you from them for your inheritance, then you shall present a contribution from it to the Lord, a tithe of the tithe. 27 And your contribution shall be counted to you as though it were the grain of the threshing floor, and as the fullness of the winepress. 28 So you shall also present a contribution to the Lord from all your tithes, which you receive from the people of Israel. And from it you shall give the Lord’s contribution to Aaron the priest.
You know which one the pastor will be preaching the next Sunday, and the next and the next.