Arsenal
Arsenal need to improve their attack, and make sure to score as many goals as the opportunities as they create. If Arsenal gets a good striker in the transfer chance and get reinforcements in some other positions in the team, their chances of doing very well in the champions league round of 16 more than they did in the group stages will be higher. I see Roma coming to the champions league next season, I see Mourinho as someone with a plan, they look to be on that track already to achieve that with their current position on the table.
With their current squad, it would actually be good enough if only to make it past the round of 16. But to play at a further stage, Arsenal certainly needs a sharper attack power than now. Arteta must really prepare for this. But I doubt Arsenal will get new players in the attack line in the winter transfer market this time. Because it is very rare for a club to let go of a great player in the middle of the season. Arteta might also have to think about making a better strategy from now on. Because I see that the strategy used by Arteta has not improved much from last season. I think he should be able to improvise more. Because the UCL is the biggest stage in football between clubs in Europe. So Arteta cannot waste this opportunity.