Flirting with Starbucks baristas?

For the past 2 months I have been going to Starbucks for some tea. I have frequented this location because it’s so convenient (only a couple blocks away from my school). I’m 17 and I like their tea, which is why I go.
Each time I go, I am greeted by the baristas I see often. However there ARE a few I always see that I never really converse with. One time this barista asked for my drink and I smiled at him as I would, but this time he gave me a second look. This barista usually doesnt ever notice me, just like any other barista, so I found it quite wierd that the times that I went after he got even nicer.
The next time I went there, he remembered my drink the way I like it (this is not unusual because he usually does that for other customers as well). But the times after I smiled at him, hes been even nicer each time and he even put some lemonade with my black tea without extra pay. He jokes around a lot with me now and smiles at me more and stuff like that. I also notice that hes a bit more enthusiastic while making my drink.
A couple days ago I didnt order anything and I was waiting for my friend to order. As I was standing by, he noticed me and he was like Hi! How are you??? and we had quite a conversation. He asked me why I wasnt ordering anything and I said I didnt want to spend any more money and I didnt want to go overboard with the caffine. He continued to smile at me and really joked with me that time and then, he hooked me up with a drink. He wouldnt even accept my tip!

This guy is around his early 20s and seems really nice, but I dont know if hes on to something? He hasnt done anything that would suggest anything, but hes just been light weight flirting with me. Yeah he is good looking and genuine enough not to seem like hes just using me to get in my pants. Am I wrong to be flirting? THOUGHTS AND OPINIONS?!?!