New mom needs advice

Hi , new mother here , both my sister and my mother passed away years ago so I'm learning things about how to take care of my baby as I go , my little one is 4 months 1 week old now so I'd like to know when is it the right time to introduce him to solid foods , he's only breastfed and he will be going to creche soon because I don't have a carer or nanny for him ... I'd like to know if it's also the right time to introduce formula because I'm struggling with pumping enough milk for him when I'm at work and which formula brand should I consider?