The best machines are Necchi brand or pre-1976 Singers.
Almost all of the machines on the market now are filled with cheap plastic parts and have 90-day warranties. Before 1976 the Singers had all metal parts and they are workhorses! If you know what you're looking for you can find them in sew and vac repair shops for $50-$100. I bought one with a cabinet when I was 17. All it could do was straight stitch and zig-zag, which made it very uncomplicated for a beginner.
As I got older and more experienced, I wanted more stitch options and features and I was disgusted with the cheap crap on the market, I wantes something that will LAST. The Necchi machines are competitively priced and the best part is they have the all-metal parts inside and have a 25 YEAR WARRANTY. Did you hear that? 25 Years!!!!! My Necchi can stitch through 8 layers of fabric without balking. Google Necchi and see if you can find a supplier - don't panic by the listed retail - no one ever sells a sewing machine for actual retail.
I'm still hanging onto my old Singer, it's still going strong and I plan to teach my girls to sew on it.
PS. Get a drop-in bobbin, if you can. Much easier than traditional bobbins.