How many reputation stars do you have?
In your situation, I would focus less on the Champions League (be realistic, you probably aren't going to pass the early-knockout stages this year) and more on getting quality backups. If your squad is good enough to win the Europa League, your first 11 is more than ready to get a top-4 place next year as well, and you need to get depth in the squad to make that consistent. If you qualify for the Champos next season as well, your reputation will certainly increase and this time to the point that you can make big-money signings.