After the 1st season, there's no real reason to wait to boost.
The basic formula is
Create day 40-48
Boost to L4
Do not boost in the regular season 1st year
If the playoffs are super important to your team, then boost. If not then get more training done before Boosting.
With this formula you'll end the season at L19 instead of L18 +xp.
Other than that, the benefits of playing boosted will out weigh xp gains.
Once you become super high tech, you'll find that it's better to time your boosts to coincide with training gains, but don't worry about that too much right now.
and as stated before... as long as you boost every season you'll hit max level 79 any way you go.
