I didn't answer, because I wasn't sure x) I have never caught a Ghost type before the first gym, but I'm definitely no expert so I could be wrong on there not being any before the first.
And I'm still not seeing Petilil /: I changed to different days and weathers and it wasn't there in windy, clear or rainy weather. So I'm back to checking my sunny day and I'll try different hours. If I still can't I'll probably go ahead and pass on searching for it actively for now. Thank you all for the help. <3
Edit: Yup, tried different hours and still didn't see a little Petilil. I'll just hope I can find it in passing one day when I go by the area.