Pick one of the popular auxlangs. ‘Nuff said about those, everyone already knows Esperanto exists and has fans in many cities worldwide.
Create your own? This is the most work. You will have the most flexibility with regards to how you use the language. You will have to promote and build the community yourself. A pre-existing conlang often is reasonably complete, has a community and prestige. Achieving that all on your own is a lot of work.
Things to Consider when Shopping for a conlang to study
You know how much time it takes to learn a language…poorly? It takes a really long time.
Is it complete? If its complete, then one needed worry about conflicts with the creator as you and the community argue over what is a mistake, what is correct and what is an innovation. If the language is grossly incomplete, see if the designer wants to collaborate. Otherwise fork and create your own.
Was it ever intended to be humanly usable? If the language requires sign language using alien body parts, supersonic screeches and subsonic rumbles, or is ludicrously difficult then just read the grammar and be entertained.
Does the author have or imagine they have extremely restrictive intellectual property rights? Don’t be thinking about posting too much Mandolorian on your blog or the fanfic police will be on your butt. There are enough language to pick from to bother with highly proprietary conlangs. Look for conlangs that are in public domain or at least a fan friendly license, like GNU or Creative Commons.
What are the talking points, what is the prestige factor, what is the goal?
This is sort of like the same question on must ask when picking a natural language to learn. Esperanto offers world peace, Lojban offers clear headed thinking, Klingon offers a deeper connection to the Star Trek fans–which is something valuable since Kirk doesn’t exist and Leonard Nemoy probably won’t be hanging out with you for beers after work. Many constructed languages think they are all things to all people, I doubt they are. Think critically about the value proposition that is floating around for a language, make sure it fits with your life goals.
Exactly who is the community right now? Depending on the language, the community of a conlang (or auxlang) is :
- intellectuals– “The only thing between us and world peace, truth and beauty is the morphosyntactic alignment of all these illogical, nationalistic, patriarchial, depressing natural languages…and the glasses I’m wearing”
- linguists and polyglots– “Hmm, ergative, lots of plosives, but still looks like Samoan”/”… and now I’m speak fluently 14 languages! (but on this language no one can call BS because no one else speaks it, mwah ha ha!”
- fringe elements– “I’ve got tattoos, I’m a member of the radical left/right, and I speak a language that you suburban clones don’t understand.”
- science fiction and fantasy– “A 3 hour 3-D movie isn’t immersive enough. Gimme the body paint and a dictionary and lets go LARP in the park”
Constructed languages do attract their target audience– if someone proposed a compilable conlang that was practical to speak and write business application in, then at least some software developers would show up in the conlang hobby universe. Speaking of which, wouldn’t it be great to turn COBOL into a language that one could use for conversation?
Are the community and the language designer getting along? Language designers can abandon the project, move on to another, make changes that only some of the community will follow leading to splits, etc. If your the 2nd language learner, you may also become the designer, promoter and so on if the language is abandoned in an incomplete state. Community schisms are interesting, too, and sometimes not. Imitation conlangs are a sign of success, but successful imitators split the community and make it hard to decide which community will survive.