I agree with you, that there is a luck in the competition but if any team fail to display quality performance from the beginning of the competition to position in a good position, I think it will be difficult for such team to experience the luck from the competition, because it go along with the team experience. For example, Real Midred that won last champion league title, I can still remember that many people thought that Manchester city or other teams will be the one to win the title but based on Real Midred preparation for the competition and their performance from the competition made them to embrace the luck from the tournament last season. That is what is still going to happen in this season, because the smaller teams are not ready to purchase some new players to boost their performance which it will be difficult for them to experience the luck in this season again.
Luck in football doesn't work the way many people take it to be. Luck always work with your efforts and readiness in most football competitions. As a club, you need to build your squad depth to be strong enough to compete with other top and elite clubs. You must not have a club full of star players but you only need a team that's competitive and believe in themselves as well as the manager.
I've taken a cue from the last year's champions league tournament where Borussia Dortmund reached the finals with Real Madrid without necessarily having a team full of star players but a team of young talented players who understood their squad philosophy and were highly committed to the success of the each other and the overall victory of the team. That's what we should look out for this tournament.