To Toy Or Not To Toy??

I'm a first time mom of a handsome 2 month old.... Sadly, I'm returning to work soon and will be LO with my parents.... I have been struggling to identify useful and developmental toys for my baby. I don't want to continue to buy various rattling toys, bears, etc..... Any recommendations on what to get to help with his development.... What did you do to help your baby reach their milestones in a fun way??