Very similar to you I only used watercolors for years and bought the starter set from M. Graham and a cheap set from Arteza. I really wish I had not bought the Arteza set and instead just the M Graham and one or two other tubes as needed. I really like M. Graham and have a few holbein colors too which are prob what i'll use going forward. https://www.amazon.com/M-Graham-2-Ounce-Gouache-Primary/dp/B0044TTG76

I think it's a solid set of colors to start and mix from. I think I bought a burnt sienna next and a different brighter and warmer red, but this should be a really good start. I do wish I had bought a bigger tube of white right off the bat since you use so much of it too.