If you feel you really need more practice, and you are OK with prolonging your practice period, then you can do an "introductory price" for a period of time, and make sure it's fully stated that this is an intro price, and not regular price, on your FB booking page. I do my mum's nails for free, she's the only one who gets them free. My friends have to pay, although I used to give a close friend a slight discount until she took more and more advantage and avoided paying altogether, which was an eye-opener to me - which means I do not book that person in anymore!
In the month I was practicing before my exam, I think I did 3-4 friends/family, including my mother ofcourse, but the rest (20 or so) were strangers I found on Facebook Marketplace, and some stayed with me after I qualified, as regulars. I also charged just under half regular price during training, and did this from home. I took photos of every set (sometimes before-afters too) and kept the ones that turned out OK. Since you are qualified now, you shouldn't be charging peanuts, but you can try an intro-offer for a set period of time. It really depends how you feel... If you really feel you need a lot more practice and not ready at all, then go ahead and ask on FB market place for some models who pay only for products/token fee. If you feel you need only a bit of practice until you get more hang of it, then I'd recomment an intro-offer. Don't sell yourself TOO short. ^_^
