Skip first line in import statement using gc.open_by_url from gspread (i.e. add header=0)

Looking at the API documentation, you probably want to use:

df = pd.DataFrame(g_sheets.get_worksheet(0).get_all_records(head=1))

The .get_all_records method returns a dictionary of with the column headers as the keys and a list of column values as the dictionary values. The argument head=<int> determines which row to use as keys; rows start from 1 and follow the numeration of the spreadsheet.

Since the values returned by .get_all_records() are lists of strings, the data frame constructor, pd.DataFrame, will return a data frame that is all strings. To convert it to floats, we need to replace the empty strings, and the the dash-only strings ('-') with NA-type values, then convert to float.

Luckily pandas DataFrame has a convenient method for replacing values .replace. We can pass it mapping from the string we want as NAs to None, which gets converted to NaN.

import pandas as pd

data = g_sheets.get_worksheet(0).get_all_records(head=1)

na_strings_map= {
    '-': None, 
    '': None
}

df = pd.DataFrame(data).replace(na_strings_map).astype(float)