Judging by an answer provided for a question below, "me gustaria" is equivalent to the three "queria" forms. That's good news because I've been using "me gustaria" most often. Should that be added to the examples in this lesson?
Also, does this lesson imply that the above three forms are more polite than simply "quiero?" I've asked many here in Colombia about this and they all say that "quiero" is much more common than "me gustaria" and not considered impolite. But still, I have trouble making myself say "quiero" so i usually say "me gustaria." Maybe I should start using "queria."
I guess I have a lot of confusion around "quiero" vs. "queria" vs. "gustaria" and their proper grammar and appropriate usage.