Apart from at higher levels the draw you get in the Cup will be determined by the top 14 players you have when the draw is made (downtime). At most levels (except for Gert) its not the level of the teams that makes a draw bad its the scope that this allows those higher levels to improve their teams from crappy 3* to Superstar 5* s
The ideal scenario is to have a crap team at the end of the season and improve it as soon as you can in the new one. But that can cost a lot.
Imo, the big "no-no" is improving your team at the end of the Season. Don't do it. The higher quality your t14 team the worse you make it. (But also if you have a low quality team then you will actually be one of those high level feared teams. >.<)
Generally, the best time for new players is next season after the rush, unless you want to be part of the rush. If it is a Quality based league draw then even Day 3 might become the new Rush Hour II