Lucid dreaming is supposed to help to connect with a spirit guide, also meditation can help to connect with one.
Just remember that it is an element of your mind manifesting itself. I have met my spirit guides (and my ego at a seperate time), not in a fully lucid state tho. They appear differently to everyone, apparently to most people they are something/one symbolic to them. In my case they are these three white "lights", except they arent actually lights they are holes in the fabric of the dream to this intense burning white space behind it. Try meditating while you dream. My (very spiritual) friend says its awe-inspiring. unfortunately I dont have the discipline to learn to meditate even in real life.
there's no gotta. there are things that work better some ways then others. and sure, there's lots of neat fun invisible stuff. just try to remember that none of it/them, is/are, in any way obliged, to resemble anything anyone pretends to know about it. the closest thing to a "gotta" is that what we screw up for others, is screwed up for ourselves as well, so it's probably a good idea to avoid doing that. as for invisible friends, there are a lot of different ways different people in different cultures have traditions about going looking for them. so i won't say there's any one way about that, because there isn't. whatever purifying yourself means to you, that's the general idea of what's involved in seeking them out. but really, who or what you're meant to meet in dreams or elsewhere, will more likely then not happen anyway.