Dale explains it correctly. Its appropriate to put enough sources to "prove" your case, and I usually keep adding things as I find them. Recently I was adding yet another source to a grandparent who was quite well documented, that her mother's maiden name was also entered. Previously we hadn't been able to find it, so it was quite exciting to find it sitting there, plain as day. I sourced it for both of them.
Dale is also correct that Ancestry.com isn't actually considered a good source when cited all by itself as the documentation provided by its members is often a "he said/she said" rather than an official document. If I'm going to use its information, I try to tease out the original documents like US Census material, copies of family Bible pages, birth certificate, immigration lists. If those materials come from "ancestry" I don't have a problem with using them.
For me, its a matter of primary vests secondary sources. I'm willing to use secondary materials if that is what is available. But misinformation gets copied from one place to another. (And, I've enough Scottish blood to absolutely hate paying for information that I can get for free elsewhere. )
I use familysearch as each entry points to an original document. And familysearch is free. I like, okay "Love" free.
Hope that helps. Backing up Dale's statement which hits a bull eye for being correct. And don't forget, with Wikitree, although the ancestors closest to you may be bought of as "yours" actually they are "ours" in that our goal is to connect each profile to the next to become one large human family.
We are all in this together!
