Promising and auspicious are used to describe a thing or person with qualities that lead us to expect they will turn out favorably. A promising first draft possesses elements that, if developed, will constitute a good paper, and people have high hopes for a promising young man or woman. The optimal time to be promising is, of course, at the start (a vacation off to a promising start). Auspicious start is also common usage, and can be used synonymously. Strictly, however, auspicious means “boding well,” as if foretold by an omen. An auspicious sign bodes well for something or someone. Auspicious is frequently used to describe times: an auspicious occasion, day, or moment. Here it suggests that the outcome of something is lucky, well-timed, or favorable at that time. In usage, the meaning of auspicious varies between "promising" and “favorable for.”
Give and bestow refer to presenting something voluntarily to someone, without expecting anything in return. This is the primary definition of give, which we use with “gift” and “present,” or the specific item given (I’m giving her a bike for her birthday). Bestow is very similar to give in the action it denotes, but it is generally used for intangible or unspecified treasures that can’t be bought, such as blessings, honor, grace, gifts, wealth, title, or authority, which are bestowed on or upon someone, often by someone in a high position–God is frequently the subject of bestow. Bestow is an elevated, formal term which can have a ceremonial feel of past eras, but you will encounter it adding nuance to more ordinary acts (bestowed a kiss on his cheek, bestowed a radiant smile upon her guests).
Letter and missive refer to a written communication addressed to one or more people normally sent by mail or email. Letter is the general term and is used particularly when the message bears the conventional format of a hand- or typewritten letter, rather than being an email or text. Missive is a rather formal, less familiar synonym for letter, often used for an official or public communication (the CEO’s missive to shareholders), but it can be used for any message or announcement that is directed towards an individual or group (the latest in a string of Twitter missives from the Governor). It’s not entirely clear why missives are more often said to be “fired off” than letters are, but its shared root with “missile” (miss- meaning “send”) may have something to do with that.