It might seem apparent, but there is a clear virtue to using your financial muscle. In three finals of the past decade, the more expensive squad (starting XI) lost just three times, and only one of those was the costlier in terms of 23-man and starting XI: Man United (£188.7m) in 2008-09 to Barcelona (£123.8m).
Teams with the fewest loan players or free transfers in their starting XIs won eight of the past 10 UCL finals. (All 10 winners, however, had the fewest loans or frees in their UCL squads.) It might sound strange but it fits with the above concept of investing heavily in talent. Juventus put up a valiant fight in 2014-15 with five frees (Andrea Pirlo, Rubinho, Paul Pogba, Fernando Llorente and Kingsley Coman) and three loanees (Romulo, Roberto Pereyra and Alessandro Matri) in their UCL final squad but, ultimately, teams that develop their talent over time naturally do better. There is no cheap and dirty path to success in Europe.
Broadly speaking, teams that cultivate their stars from an early age do reap bigger dividends in the Champions League. Seven of the past 10 finals have been won by the side carrying the most players from their youth system in their UCL squads. Only twice did the academy-heavy side lose and both times, it was Bayern Munich (vs. Inter, 2009-10 and vs. Chelsea, 2011-12). It's worth noting that in those two finals, the vastly more expensive team (see Tip 1) won.
Barcelona are famous for having a stable of long-serving players over the past decade but it doesn't really translate as a tangible advantage in the Champions League. The teams with the longest average time at the club (per player) won five and lost five of the past 10 finals, offering no discernible edge. However, all 20 teams to make it to those finals had long average times at the club. Man United's losing squad in 2010-11 averaged 5.9 years per player while their starting XI for the final averaged 7.2 years at Old Trafford.
There's something to be said for experience on soccer's biggest stages, but not too much. By only half a year (26.8 to 26.3), teams with older players win the UCL final, but the number is skewed by Milan (average age: 30.3 years) beating Liverpool (25.4) in 2006-07. Five of the past 10 finals were won by the younger team.
Though there is no longer as much distinction between top footballing nations when it comes to style, six of the past 10 finals were won by the teams that had the most players who were born in the country they represented. On average, UCL winners had 10.2 players per 23-man squad from their home nation compared to 9.1 for the runners-up.