Corelle are great, I see them often at thrift stores for cheap.

We did a 2 year RV Life adventure, and needed plastic microwave safe dishes. We found some at Target, I think they still sell them, pretty colors and they were like $0.79 each. I think Walmart has them too. Daiso (Japanese Yen store on West coast) also used to have plastic large ramen bowls and wood-look large oval low bowls that we used for salad and burrito bowls. Oil and tomato (acid) based sauces always etch and pit most plastic when heated in the microwave, best to use glass or Corelle for things like that. Silicone is also good in the microwave, we had some collapsible food containers that worked great for the RV in terms of space, bonus is that they are nonslip in the RV fridge!