For a tiny language, I really like toki pona, but it's meant to be a minimal artistic language, more than an IAL (international auxiliary language).
Last I checked tho, Globasa looks really interesting. The way that they add new vocabulary, and have a good representation of world languages, seems to work well.
Esperanto is also good, but when my partner tried to learn it, they were weirded out by some of it's quirks, like noun declinations based on whether it's a subject or object, that seems unecessary.