org-capture-templates probably has the densest doc-string of any variable. The way I deal with it is figure out what I need to do, do it once and then never change it :-) The downside is that when I need to change it, I find that I've forgotten everything so I need to start from scratch. But after doing it a dozen times or so, the relearning gets faster and easier. In short, hang in there!
For the time stamp, you can either use
%t which provides the date in ISO format, or you can use
%<%Y/%m/%d> as the doc string of
%<...> The result of format-time-string on the ... format specification.
The level at which the capture is entered for an
entry type is again described in the doc string:
... Will be filed as the child of the target entry or as a top-level entry.
Since you are not using a target entry, it is filed as a top-level entry, no matter how many stars you put in the template. See the
target description in the doc string.
You could create a top-level headline, say
* My daily thoughts in your file and then use
... (file+headline "~/notes/daily.org" "My daily thoughts") ...
instead of the plain
file entry: the captures would end up under that headline.
There is plenty more in the doc string to keep you busy for a while. Start simple, experiment, ask questions: you'll get there.
BTW, to get the doc string of the variable, do
C-h v org-capture-templates
and if you don't know yet how to use the emacs help system, do
C-h ? and learn how to use it ASAP!