u can take a look at my roster and depth. u need 6 trainees for ur 1st season in Div IV, save ur money buy 1 big FA for ur second season and u r good to go.
also expand ur arena.
This.
As I understand, and what I am currently doing, is that 1st season in Div IV is developing trainees and expanding arena constantly. This season my arena has expanded almost 1500 seats, and as a result my gate receipts up almost 30k per home game. Also trainees. Throughout Div V you found your trainees, and maybe got a season of training in. Well first season in Div IV is also a season to focus on developing your future core players.
Season Two is where you want to try and prepare for making a run for a championship. Depending on difficulty of your league this may or may not be as easy, or as quick as you think, but nonetheless this is a season where you want to continue training your 20-21 y/o's, and save up the money that last season you would have been using to expand your arena, to find players that you think could help you make a championship run. These players are usually 15k+ in salary and balanced, and not one dimensional. Defense is key in Div IV so look for that in your players. Also backups are important, and gameshape is critical in Div IV.
Again that is a path I am taking, and a path that people before me have taken and succeeded in doing. One thing I am doing is selling my draft pick(unless of course it is simply amazing) so that can give me an extra 300-1+ million to use spend on my roster.