Predicting a champion in league is completely hard, but usually it's not away from the top 3 favorited teams. But I'd consider to bet on a match, not predicting the champion.
Not only the Champions league, predicting any sports isn't easy at all, because even games with low odds can lose, how many times we have seen our parlay lose by 1 match, it's really common.
Personally, I like to bet in UFC because the fights are fast, you don't need to be waiting a long time to see your bet results, and since it's a 1 vs 1 sport is common to win with the underdogs, you only need to see one good punch to turn the odds in your side.
It is, there is a big chance that you could lose money if you gamble on the favorites all the time. Lets take the week in and week out situation, there are 5 big leagues, gamble on every game that has favorites under 1.50 odds, there would be a few every week at least, sometimes even more.
By the end of the season, do you think you would have a profit or do you think you would have a loss? I can't guarantee anything, of course if you are lucky then maybe you would end up with a win but I think it is quite obvious that you could end up with a loss as well. Even this uncertainty provides proof that you shouldn't expect to make money just because you gamble on the favorites, it is not a sure thing and you may end up losing sometimes.