It's important to get a high fan factor since it influences your income during the games to come. Don't buy a 12th player or an extra reroll, but increase your Fan Factor, it will pay back over the games to come earning you the new players and additional rerolls you need.

Another way of seeing it is that money simply bloats your team rating. Teams with high AV and/or regeneration might be able to get by with a slightly lower starting Fan Factor as these teams have less use for money. It will usually result in a team where you have more SPPs (and skills) than your opponent. However, I recommend to not start with anything lower than a Fan Factor of 5. / Christer

Another minor thing to consider is that a lot of people prefer to play against teams with a higher fan factor. Yes, it's more likely to mean that the Pitch Invasion works against them, but higher FF means a higher Gate and more money for everyone. Anything that helps get a game is a good thing and if you can contribute to rebuilding the team you just destroyed, all the better. If you have a bunch of positional players to fill in or RRs to buy up, don't underestimate how important earnings are. - BadMrMojo -

Not to mention that each kickoff roll there's a 5/18 chance (28%) of getting a result you can turn in your favor, instead of against you as is most probable if you have a low fan factor. During games with many kickoffs this alone may pay off. - Humbe -