I am going to disagree slightly here. While going after too many recruits too early will spread yourself way too thin I feel that once you have 6 guys signed if you only go after 9 more then you are basically wasting an hour per week.
Even if the recruit is a longshot to make the team you might as well sign him and give him that longshot. If the player can come in and improve your team in any way then you might as well sign him. This is especially true with lower rated teams where it is pretty easy to find a player who will atleast be the best player on your team at his position at atleast one usefull skill or someone who can add valuable depth to your team.
Also, you can even sign more than 25 recruits although anything beyond the 25 will be usually very low rated. The thing about it is if the players are on your board when you sign your 25th player it seems to drop all their interest so they have to be players you can add after that and still sign. That said, if you sign any player, no matter how low their chance of making your team, there is still a slight chance they could improve your team so if you have the minutes use them