[jonathanjaeger]

I do daily 30-60 minute conversations with native Brazilian speakers on Italki. That can add up in price quickly, but I would recommend at least 1-2 lessons per week to start after getting the basics down on something like Duolingo/Rosetta Stone. It was a world of difference between year 1 only using Duolingo/YouTube etc. and actually having Brazilian teachers correct my grammar, pronunciation, and add vocabulary for very context-specific situations that came up in conversations. Not to mention slang, idioms, etc.

[ablekh]

I see. Thank you for your prompt comment. Just one clarification ... When you are saying "getting the basics down on something like Duolingo/Rosetta Stone", do you mean that "basics" here includes all levels (as far as I know, solid courses like Rosetta Stone or Fluenz - as opposed to Duolingo and similar apps - have multiple levels, where higher levels are pretty advanced) or you are talking about first 1-2 levels?

[joshvm]

Duolinguo is a poor substitute for human interaction. It's a good tool to support other methods, but it encourages pattern matching rather than actual memorisation and there simply isn't enough variety in the examples to help you with translating unseen phrases. It's also not sufficient for speaking practice, but at least you can hear the text-to-speech.

There are some positives. The community is very active and helpful. They've done a lot better with the lessons. Japanese, for example, is much improved. It used to be that you'd get exercises in hiragana with no context at all.

I agree with the other post, you'll get much more out of a two hour class once a week than doing ten minutes of duolinguo a day. The claim that x hours is equivalent to a university semester is nonsense.

Your question was about optimality. It doesn't take much classroom time to get good - maybe two or three courses? (say 60 hours to A2/B1) That gets you enough of a baseline that you can start watching TV, reading papers. For example in our B1 lessons for Spanish, we'd actually read El País as an exercise.

[jonathanjaeger]

So I went through the whole Duolingo tree for Portuguese and thought it was high quality and got me good a foundation. As others noted, there is no substitute for actual conversation/interaction with native speakers, and I wish I started that sooner. I also second the recommendation of using something like Anki or Quizlet for vocabulary practice. I only noted that it's good to have a base before starting with professional teachers because if you're budget isn't unlimited, you might not get the bang for your buck having teachers walk you through the most basic stuff like hello/how are you/how much does that cost/etc. that you can get with Duoloingo/Rosetta Stone or similar programs. But if you want to start off with Italki and lessons on day 1 with native speakers, it certainly won't hurt!

[mantap]

Duolingo works very well as an introduction so you can get a taste of a language.

There's no point doing higher levels on duolingo - if you actually want to learn a language to conversational level and beyond then proceed directly to memorising vocabulary with spaced repetition software such as Anki. It is much more effective.

The person who might benefit from higher levels on duolingo is the traveller who does not aim for conversational level but wants to pick up enough words to get by.