The holiday of Shabuot is included among the three "Regalim" ("pilgrimage festivals"), when there is an obligation of Simha – to rejoice and be festive. The Gemara says that according to all views among the Sages, there is an obligation to enjoy oneself on Shabuot. Beyond the spiritual enjoyment that we experience by studying Torah, there is also a Halachic obligation to rejoice through physical enjoyment. The Sages teach that for men, this means indulging in meat and wine. Although there is a widespread custom to eat some dairy meals on Shabuot, one should make a point of eating meat on Shabuot, as well. One can fulfill this obligation with red meat, which resembles the meat of the sacrifices that were brought in the Bet Ha’mikdash on the holidays, or even with poultry, if that is what he enjoys, even though it does not technically qualify as "meat." If a person does not enjoy meat and wine, then he should eat whatever foods and drinks he enjoys. There is certainly no Misva on Yom Tob to eat foods that one does not enjoy.
One is also obligated to make his children happy on Yom Tob. The Rambam (Rabbi Moshe Maimonides, Spain-Egypt, 1135-1204) writes that this is done by giving them treats, candies and the like. The Misva also requires making one’s wife joyous, and the Rambam writes that one should purchase new clothing or jewelry for his wife before the festival. If one’s wife does not need new clothing or jewelry, then he should buy her other gifts, even fine foods and the like.
It is proper to immerse in a Mikveh on Ereb Shabuot to purify oneself in honor of the festival and in honor of the commemoration of Matan Torah.