Col, the problem is that 'like' in English can mean, like, several different things, depending on the context. The problem with online/machine translators is they don't understand context, and so often get the wrong meaning. So, if it's any help:
'Gustar' is 'to taste', like French 'gouter' (there's another use of 'like'). The English equivalent, 'gust', is now archaic, though the opposite, 'disgust', is still going strong. 'Me gusta' means 'it is tasty to me', so 'I like'; 'no me gusta' = 'I don't like'. It does not normally mean 'I would like', which is a polite way of saying 'I want'.
'Quiero' is from 'querer' - etymologically 'to quest', so 'quiero un cafe' means 'I'm looking for a coffee'; 'request/require' is from the same root, so if you think of 'quiero un cafe' as 'I request a coffee', you're not too far wrong. 'Querer' is widely used in Spanish as a general-purpose 'want/wish' sort of word, so this is the 'I would like' sense of 'like': 'si quieres', 'if you like'; 'quieras o no', 'whether you like it (would wish it) or not'; 'quiere ser medico', 's/he wants/would like to be a doctor'.
As for the personal pronoun, 'yo', 'I', this is rarely used in Spanish, normally only for emphasis or to distinguish 'me' from someone else: '¿quien es? ¡Soy yo!', 'who's there? Me!'; 'yo soy el culpable', 'I'm the culpable one' = 'my fault'.
In Spanish, as in English, you can come up with all sorts of flowery phrases, like 'I wonder if I could possibly trouble you to be so kind as to bring me a coffee'. Spaniards are a courteous people, and some might enjoy this sort of thing, but unless your Spanish is good enough to carry on a conversation in the same vein, learning phrases like this is a waste of time, as you won't understand the response. Language is primarily about communication not about producing beautifully turned phrases, so, as others have said, 'a coffee, please' or 'un cafe, por favor', will do the trick just as well. And if the waiter says '¿Como quiere el cafe?' that means 'how would you like your coffee?'