These resources are my product and service recommendations for my students. It is by no means a complete list and I will add to it as I come across new things.
Disclaimer: some of these links are affiliate links. I only recommend products I believe in.
Sharmusic.com has a wide selection accessories and the best selection and prices for strings. I recommend Larsen strings in Forte gauge for A, D, G, and C strings. Another setup would Larsen Forte for A, D and G, and then Thomastik Spirocore tungsten C string.
Locally, Weishaar Violin Shop has competitively priced strings.