A social situation that I don’t know how to handle

I (18F) have been talking to this guy online, who I know from a club we are both in at school. We have interacted in person once. He asked me whether I wanna meet up and smoke weed later this week cause he got some. This was a follow up to a conversation we had on 4/20 where we joked about weed and I probably made it sound like I’m more experienced than I am (in reality I’ve been high like once lol )

I think I should decline considering I don’t know him well and I haven’t smoked many times before. But I’m trying to determine how to respond without making it seem like I never want to talk to him, I just don’t know him that well to feel comfortable in that situation

Update: I responded I just said I couldn’t this week bc I had to study for finals, and asked whether he was going to the club meeting this week