About learning kanji... I find I can learn them pretty quickly, and my method is similar to Kohlrak's but not quite the same. I have to say I am so far away from experthood that I can't see it with a telescope, so take my 'method' with as much salt as you like. ^^ Using my trusty 'Kodansha Kanji Learners Dictionary' (which I have become inordinately attached to... XD), I just copy the kanji, and put it in various of its compounds, using kanji that I know already. This helps me to remember the pronunciations of all the kanji involved in the compounds! ^^ (For example, it's easy to remember 'yuki' for snow, and if I learn the word 'setsujousha' for 'snowmobile' then I can easily remember the three kanji of 'setsu', 'jou' and 'sha' and their meanings. ^^)
This way, I can usually learn about 4 kanji a day at a reasonably steady rate, assuming I'm studying every day and concentrating.

Although sometimes one or more of their readings escapes me the next day and I have to go back and relearn them. Of course, I have to keep revising stuff as well until I'm sure that it's stuck in my brain.
As far as making up words goes... Personally, I love 'invented' words! But you have to be aware that they aren't real words, too! I like invented words because despite the fact that most of them are 'silly' made up stuff, either because someone isn't a native speaker or because they're just having fun, still, it is in ways like this that language does evolve. No, you can't say that that is evolution of the language, but it is in such ways that it happens.
As someone pointed out, the 'gust' of 'disgust' bears a strong resemblance to the French 'gouter' (sorry, this machine won't do accented characters ><) and probably derived from this word (or from a common root, I'm not sure). There are still related words in English, such as 'gustatory'. So I think at one time 'gust' on its own was a word in English, but it fell out of use and only the compound 'disgust' remained.
EDIT: I just realised I invented the word 'experthood'.
