I would say dont worry about IDPs until only sleepers are left on offense. The difference between the best and worst starter in any IDP category isn't too much, and lots of guys go way too high because they're great NFL players, but not good IDPs. I say build your offense, then just target the best available MLBs, SSs, and if you must start DLs, under appreciated DEs like Aaron Schobel, etc. Fill in those positions in this order: LB (consider them the RBs of IDP), SSs (They're your IDP WRs), DEs (they are IDPs equivalent of a kicker).
You can search around the site for more in depth tips on IDP drafting, and I suggest doing so. Having a leg up on knowing how to draft IDPers can lead to having a superior offensive squad, and not wasting picks on big name defenders who arent great as IDPers.