alright I'm about to fucking chill

What is the /fit/ recommended weight set? I was going to buy weights for a home gym and I want to make sure the materials are good enough (steel or iron). Seems like some options on Amazon have sets that use plastic parts. I will probably buy a set with 90 lbs to have up to 45 lbs per dumbell. I tried checking Craigslist, but everyone is selling weights that are over the price of amazon, so used weights are not an option.