I should know about this as I have soon recorded them all.
I think the right way to start is actually no.1 in C major which also is among the easiest. But no matter how easy these inventions looks at a first glance, they are actually harder to execute than most people think. At least for someone like me who are not used to play counterpoint. It is not so much that they are difficult to play but rather difficult to memorize. An option to no.1 is the D minor or the B-flat major.
The ones I would not start with is the A minor or the F major which in my opinion are the more difficult. The F major (actually a little Toccata) is perhaps the most famous but requires a lot of different technique and is difficult, especially in the later passages for left hand. When you can play the C major, D minor and B-flat major, I would continue with the G major, C minor and D major.