Another stupid question: Witch material to choose???

Hi guys.. I have no clue about studio DIY:) I read here for 4 weeeks.. tow questions are not answered yet!! For Insulation I choose massive material like MDF, Heavy rockwool or fibreglass pannels.. If it's not necessary to Isolate anything (only acoustical treatment of a room) what material I choose then (AND WALL CONSTRUCTION) Second: Door: How to get it Isolated!!?? Everyone is using doubledoors?? sorry again for these stupid Q.. but no answers found

some adds... For Insulation: Constructed wall out of MDF - Fibreglass/Rockwool - Rigips(plasterboard) For accoustical Treatment: Rigips(platerboard) - Rockwool (Rockwool has to be towards the room)

I forgot working today.. and.. I read 100'000 posts on this great site.. men.. life sucks.. I spent now 7 years of my life to be a demo-producer and livemixer. & I see, It will take me another 7 years to get a "HALF decent room".. it's not the budget now that makes me feel ill, it's the amount of knowledge I need to have... too much for today.. maybe tommorow it will feel better.. I found this http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2125 and a lot of questions are covered... thanx so far.. I need time till tommorow for some serious relax-sessions at home;)

Hang in there, George. No pain, no gain! 8)