Best place to buy seeds

Hello! I am planning on doing my own large garden this year. We are planning on having a lot of different plants. Where is the best place to get seeds? Are the packets at Walmart the same quality as seeds from websites like living seed company?

Thank you in advance for any advice. Also, I was wondering if anyone could point me in the direction of good websites or books I can read that will help me learn more before I start the garden this year. I have done some research but I want to try to do my best to have a nice garden!