I used memrise to get pretty darn good at Korean. I mean, I’m not fluent or anything, but I can do like 80% of things without begging a Korean person to help me. I’m using it for Japanese right now…for reasons. Basically, it uses spaced repetition and a gamification system to give you points (which are completely meaningless unless you compete with your friends). You’ve got to do grammar on your own, but as far as I can tell, this is the best way to learn vocab that I’ve come across. You can pay for the premium membership if you want, but otherwise, it’s free and you can just sign up with facebook. Many content. Very recommend.