well, you are here on lingq so why not just try checking out a bunch of them in the drop menu? It is more important to go with a language that you have fun with: enjoy the sounds of, enjoy looking for content, getting excited of the prospect of visiting that country. You really can’t go wrong, trust me!
Ok, so I will give you a quick overview of some of the differences in learning different language. I’ve put a least some time in just about each of these languages so here is what you can expect in terms of difficulty.
I broadly put languages into 3 categories for native english speakers.
1. The "easy" (better said, more similar and less difficult)
Dutch
Swedish
Danish
Norwegian
French
Spanish
Italian
Portugese
Romanian
Have some similarities and common origins from English. These consist of European romance and Germanic languages.
These are definitely the ones that you will be able to learn the fastest as there are many many similar words, it uses the same alphabet and the most familiar grammar and sentence structure…
2. The butt-numbingly difficult ones.
Korean
Japanese
Arabic
Chinese (mandarin or Cantonese).
These languages are very fun, .... but they are as far away as you can get from english in terms of common words, writing systems, sentence structure, and sound/pronunciation. It can be slow and frustrating in the early stages so don't get discouraged.
3. Everyone else.
Just give something that you think sounds cool a try and see if you get into it… there aren’t any binding commitments so there is no pressure to make the perfect choice at the start. Go with your gut.
" it’s much easier to reach a level in Spanish where you can converse and read authentic stuff than it would be in a Germanic … language"
Do you have experience with Spanish and a Germanic language without cases? I personally don’t, but am curious about the comparison.
I also think that Romance languages (and to a slightly lesser extent German) lend themselves to LingQ’s methodology better than more exotic languages.
But when it comes to Arabic, Japanese, etc…well, it beats me how on earth is a person is expected to get any kind of toe hold without first formally studying the structures.
To me Dutch sounds like someone choking on phlegm. Hideous stuff.
My experience is with German and Italian (but Spanish is, obviously, a quite close sister language to Italian.)
Was German more difficult for me than Italian? Hell yeah! 
Don’t get me wrong - back then when I was a young dude I simply loved learning German. But an easy pathway (especially as regards attaining any kind of fluency of active use) it was not. Declension for case and sentence structure took a lot of effort - in my case at least. And vocabulary is much harder to learn too, IMO. French, Spanish and Italian have so many more words that are already transparent to an English speaker.
Here is an example from something I happen to have in front of me right now, the label on an IKEA sofa cover, still in it’s packaging:
German: Zusammensetzung gesamt 78% Baumwolle 22% Polyester
French: Composition totale 78% coton 22% polyester
Italian: Composizione totale 78% cotone 22% poliestere
I mean, even if one has never studied French, one would have to be a real mutt-brain not to get what “composition”, “totale” or “coton” mean! But “Zusammensetzung”, “gesamt” or “Baumwolle” aren’t instantly transparent to a beginner. These aren’t isolated examples, there are many 1000s of words in Romance languages that an English speaker can pretty much immediately understand on sight.
Spoken like a real man with a lot on his plate. Total winner.
And you have followed this ‘total winner’ around and wasted your time commenting on what he has to say. Says a lot about you doesn’t it man child ?
Doesn’t your tiny bedsit need cleaning or something ? You must have better things to do than follow me around commenting on my posts. I know you’re bitter because you speak hideous caveman pseudo-French but you don’t have to troll me.
Dutch sounds bad, my French sounds bad …what sounds good to you, great overlord polyglot? After all, you are the expert here on foreign languages! Steve who?
i hope you know how to speak french and speak it well to be judging any ones accent as hideous or caveman other wise that is is nonsensical
‘To me Dutch sounds like someone choking on phlegm.’
I didn’t know your mother spoke Dutch.
Maybe he was talking to a dutch person who was actually choking? Dutch is a lot of things… but phlegmy/choking is not one of them.
+Droopy We follow and troll you because you struggle so much to sound outrageous that you en up being hilarious. Trolling a troll’s just fun!
Oh my, the forumites are banging out the ‘your mum’ jokes.
You’re like a queer little gang.
Maybe you can tell me what it’s like living in someone’s back bedroom in Russia or wherever it is you are at the moment ?
He doesn’t speak French he speaks Québécois which is like some caveman version where people sound like they’ve got speech impediments. They say it’s French because it’s written the same.
I have not been in Russia but staying with a host family when you’re a student is pretty awesome.
I guess you would know given that you know French and many other foreign languages. Following your logic, Americans speak American, Cubans speak Cuban, etc etc.