My LO is about to be 3 months next week and as his senses and abilities are increasing I want to have some toys on hand that he will like as he grows and develops. What are the best toys out there for kids 3 months and up. I have a bunch of rattles, teethers, and an activity gym already - what else should I add. There are so many options out there - I don't want to waste money on something!! TIA!!