Help- Roster Size

[WindyCityFlyerr]

I'm starting a new NFL Dynasty league. My question is: What size roster should I have to make trading effective? I don't want all teams stacked which would cause minimal trades.

I'm having 12 or 14 teams. And there will be individual D players. We are also having rookie drafts every off-season (Another possible trade option)

So what would be a good breakdown of roster positions for teams?

I hope I gave enough information.

Thanks, I appreciate it!