The Rashbam says the simple translations of סכה given in the Gemara is actual booths, however, he takes it to mean something else. Hashem is teaching, "when you have gathered good things for your house, wine, oil... you should just remember that I made B'nei Yisrael dwell in booths in the desert for forty years without being settled anywhere else. Therefore now you should give thanks to Hashem who has given you inheritance and settlement, and you should not say that because of me I have all of these great things.
The ספר החינוך explains it as we should think of the great miracles that Hashem did for us through the dessert, when he gave them the ענני כבוד and the fire at night (some explain that Bnei Yisrael made actual booths at night).
The מלבים says that the one who translated סכות as booths did it to imply that we should not fill their houses with all sorts of things because they think that this life is the end of all life, and are not concerned with the world to come. They perceived this home to be the permanent one. The סוכה reminds us to be limited with our possessions.
A fourth suggestion is that on this festival everyone leaves his money matters and merchandise and goes into a tiny booth which contains nothing more than a bed, table, chair, a lamp, and a couple of meals. This serves as a reminder to us that all we need to survive is the minimum, because this life is only temporary. The minimum area of the סוכה is 7 טפחים square and 01 טפחים high. This indicates a life of modesty, which means we shouldn't chase after luxuries, for if we are used to modesty we won't lack anything, rather if we are accustomed to luxury you won't have enough.
One message that all of the above opinions are sending is that one should live life to its fullest not being self centered, rather for Hashem's sake.