I create websites as a hobby, and I can tell you that Cotonti is one of the best systems to work with (over the years I tested quite some cms, and always came back to this one and it's predecessor LDU). Oke, the base is small, and support may not always be what you expect it to be (in comparison with the larger cms like drupal a.o.) but it's very easy to learn, and (personal opinion) in some uses quite unique (that's why I like it so much).
As GHengeveld says, it's best to use a base skin (for 0.6.20 sed-light and for 0.9.5 Nemesis) as an example and create your own from there. Those skins use the most frequently used tags, so it's a good start.
It's worth your while to give this small community your attention/love.. It will pay off..Personally I find it to be a good thing, coz the lines are quite short, and talking with an programmer which stands close to the project isn't hard at all, something that can be quite impossible with the larger cms's out there..
