Derby don't actually need many players in. Just get some of the deadwood off the wage bill.
Tyson can normally fetch about 1 million.
Adam Ledgkindz (spelling? the goalkeeper...) can normally get about 600k.
Ben Davies goes for about 200k
Gareth Roberts for 100k
Then look at bringing in some loanees. Robinson from liverpool is a good shout to fill the DL posistion.
Bring up Mason Bennet from the u18s, he is class.
Give Hendrick, Hughes and Bennet plenty of game time and they'll turn into half decent premiere league players by the second season, and hopefully by then you'll be in the premiere league yourself or ready to push for promotion in the second season. Those three will prove to be the core of your team along with Brayford and Fielding.
Derby are an awesome save on FM this year!
Good luck!