Keep track of your finance in Manager Mode in Manage Club. It will tell you your predicted finances for the rest of the season and in it's different areas. (Don't make the same mistake that I made, I thought I would end up with that money at the end of the season).
After you have completed your first season. Sign AS MANY free agents as you can be bothered to sign. Offer then the maximum wage that your club will allow you to. Play one match. You will have signed all of the players you offered a contract to.
Then put them all up for sale and accept all offers that come in for them. I usually gain about £35-40million each summer doing this.