Where do you get fashion/style ideas from

I feel like I have nothing to wear for summer. I work in a workplace that is extremely casual (jeans/sneakers) so my wardrobe is mainly made up of those types of clothes. I feel like when I am invited to a barbecue or to go to dinner with friends, I have nothing a little nicer to wear. Not only that, but I also feel like I have no idea what is in style nowadays or where to shop. I also feel like it is hard to find clothing because I'm in that weird middle aged place where I don't want to look like a teenager but I also don't want to dress like an elderly person either. I saw a photo of myself from like 10 years ago and I looked so nicely dressed and put together and I don't feel like that anymore. Does anyone have any suggestions?