You would need to become a mentor yourself to rejoin the network as one instead of a sprout.
https://na.finalfantasyxiv.com/lodes...5e17f0fd585473

Here's a website detailing it all.

However the quicker option if you're just starting the game would be aiming to be a Trade mentor. Which I believe is just getting one DoH and DoL job to 80, much more doable then the increased 1500 commendations for new players.