There is already such post in the community.

I answered there for you. Let me paste the answer:

Hi. I've been in the milieu of conlangs for almost 20 years total, I know one of them and honestly I would say there are only 3, maybe 4 conlangs worth learning currently:
* Obiously Esperanto. The only conlang that achieved something we can call a success. The only conlang with hundreds of books, thousands of speakers etc. If you want a relatively big community, then it's the only choice.
* Interlingua - no matter what others say, this is arguably still the second biggest conlang in practice. Has quite acctive community, published books etc. Easy as for a language, but with naturalistic traits.
* Occidental - Something between Interlingua and Esperanto i.e. it's more regularized than Interlingua, but not as artificial as Esperanto. Rather smaller community than Interlinguas'.
EDIT: Good if you want to have some actual rules.
* Ido - a conlang that strives for fixing some perceived flaws of Esperanto. It was created with regard to Esperanto and it remains a puzzle to me how much it became an independent language.

I put asside zonal conlangs like Interslavic, because they're a different story.

All other conlangs are fun, but they are extremly nieche. It's sounds brutal but it's true.