I can tell you from my own experience - sometimes I bet on important football matches, for example the Champions League, or the European Championships... But sometimes I get greedy and want to bet on unfamiliar events, such as the Brazilian league or something similar... That's when I realise it's time to stop! Perhaps the first sign of addiction is the emergence of greed...
I don't think it's greed? Though it could be a reason, but hey, you may just want to expand and try out other sports/events. It's nothing really new tbh, even I sometimes want to bet on eSports games that I don't really know, just because, well, I want to. Greed is a warning sign for addiction yes, but wanting to try out betting in other events doesn't seem to actually be one, nor does it equate to greed.
An addiction is a mental illness, and the major indication of an addiction is a lack of control. Unfortunately, many are more addicted to gambling more than they are willing to admit to.
This. Greed and lack of control basically go hand in hand when it comes to gambling, and it's pretty much a sign that dictates that you're closer to being addicted than you actually think so. Greed basically is the one that controls you and not really you, and that should already be a notice to yourself.