All of these are fairly good ways to make TC, however I disagree with doing loans for making TC. You are going to be scammed probably 6/10 times if you do loans (maybe more or less), if you are going to loan someone TC make sure they aren't low QI accounts as they are most likely alts of a known scammer. (staff can check to see if they are) I personally would only loan TC to clan mates or someone I've known for a while. Even though, its still possible to be scammed by them. Also make sure they seem to have a reasonable way of paying you back. Dueling, and betting TC is not a reasonable and trustworthy way of someone being able to pay you back. You may also want to look and see if they have any items worth the value or close to the value of TC you're loaning them as this can be used to pay you back. (the only dueler I'd loan TC to is Diamond but he clearly doesn't need it)

My overall advice, just don't do loans :C