i accidentally erased my mac partition
I have a late 2008 MacBook, decided to boot camp with windows 7, everything was fine until I decided I wanted to partition my existing Windows partition which has now corrupted my Mac partition and I have tried everything to get back in. There aren't any important docs or files that I need to recover as I have it all backed up but I really want my Mac OS back! I've tried to use TransMac to make a bootable USB from a Yosemite DMG I got off the pirate bay but that doesn't seem to work. And I can't find a legitimate download link from Apple since I don't have access to another Mac. I have read every forum and help guide I can find out there and nothing seems to work. I have tried holding option and all I get is the Windows boot option, I have tried CMD R, I have tried option CMD R P, I have tried from bootcamp in Windows. If anyone has a link to a usable Yosemite dmg or any advice whatsoever please help, this is the last hope I have.
Thanks in advance
MacBook, OS X Yosemite (10.10.3)