@LyndaDelph @alexhaydock I've used Babbel since I started and it's worked great for me. I might have an advantage as I took a Latin course (which taught me some linguistics, including words like "accusative") and I did the one free course on a site my friend recommended that I don't remember
Babbel isn't free though which is where Duolingo really shines, even though as you said it's not really meant for serious learning.