Generally scouting as many players to at least level 3 is my primary objective. I see the difference between scouting from level 2 to 3 far superior and more important than 1 to 2 or 3 to 4.
But given the scouting methods that we have, I rarely do individual scouting, I use my budget on all the scouting tools we have (camps, assistant search, scouting service) as this is the most effective scouting you can get for your buck per player. But the primary objective that I have my sight on with my approach is to get as many level 3 as possible, just happens that usually I end up with more level 4 than 3 so this is icing on the cake.
I usually leave a little scouting cash on the side and if there is a player who is scouted below level 2, then i may do individual scouting to 3 if I see he may be a big asset to me (distance or strong preference or no one is recruiting after him).
Bottom line: it's all about the level 3 for me.