I dont know how to do a sentence just I know that in spanish always say "le" mas verbo: ex: yo le di unas rosas, yo le dije, tu le compraste, dont´t know but le is correct. "voy" we use it with an action that we intent to do,but not already is done is the same to say I am planning. Is a verb that marks "intention" Le voy a hacer una carta, voy a estudiar, voy a comprar comida, you want to do it but you still dont conclude it. (note that my english its not well jeje), when you´re saying "le doy una tarjeta" is an action that you are doing in this moment is not a plan. [Le] always use it when you´re talking about another person with some acquaitance, you cannot use it with you never but NOTE in the second you can use "le" but in formal speech and in question.ex. Disculpe, le gusta bailar? , le molesta si fumo? refering to a person more older or a person you dont know. I hope you undestand or anyway ask me Im native, so I really dont explain with grammar jaja.