Naivety might or might not lead to gullibility. You’re not gullible until someone’s taking advantage of your lack of experience.
For instance, a naive child might still believe that babies get delivered by the stork. But that’s not a belief that’s likely to be taken advantage of. But if someone’s naive enough to believe that that guy on the streetcorner is selling genuine Rolexes, they’re probably gullible.
Try this (I’m SURE others can come up with better examples.)
Naive and gullible: Doesn’t know about something, and will believe an explanation without checking up on the source.
Naive but not gullible: Doesn’t know about something, but will check up before falling for someone else’s pitch. Will look for reliable sources.
Not naive but gullible: Knows about something, but still falls for scams about it. Overly influenced by others.
Naive and Gullible: A walking target for scams.
And…sometimes the same person can fit into several categories on particular subjects.
When a 10 year old responds to a spam, they are naive; when an 80 yo does, they are gullible.