Biblatex - add given name initial and year to style authortitle in footcite

Question

I am trying to add two things in the footcite.

1. Initials of the author
2. The publish year

The footcite should be:

1 Vgl. Gastineau, G., The Exchange-Traded Funds Manual, 2010, S. 78.

The reference page should is fine already with

Gastineau, Gary L. The Exchange-Traded Funds Manual. New York: John Wiley & Sons, 2010. isbn: 978-0-470-63734-0.

MWE:

\usepackage[style=authortitle-ibid, sorting=nty]{biblatex}
\addbibresource{literatur.bib}

@Book{Gastineau2010,
  author    = {Gastineau, Gary L.},
  title     = {The Exchange-Traded Funds Manual},
  isbn      = {978-0-470-63734-0},
  publisher = {John Wiley & Sons},
  address   = {New York},
  year      = {2010},
}

\begin{document}

Text \footcite[~Vgl.][S. 78]{Gastineau2010}
\end{document}

Answer 1

You can't easily get "Gastineau, G.", so I hope you are OK with "Gastineau, G. L.".

For the name format in the citation, you need to modify the labelname format. In order to also print the date in the citation we add \printdate to the cite macro (ll. 10-15 in authoryear.cbx)

\documentclass[ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=authortitle-ibid]{biblatex}

\DeclareNameFormat{labelname}{%
  \ifnumless{\value{uniquename}}{2}
    {\usebibmacro{name:family-given}
       {\namepartfamily}
       {\namepartgiveni}
       {\namepartprefix}
       {\namepartsuffix}}
    {\usebibmacro{name:family-given}
      {\namepartfamily}
      {\namepartgiven}
      {\namepartprefix}
      {\namepartsuffix}}%
  \usebibmacro{name:andothers}}

\DeclareNameAlias{sortname}{family-given}

\DeclareDelimFormat{titleyeardelim}{\addcomma\space}

\renewbibmacro*{cite}{%
  \iffieldundef{shorthand}
    {\printnames{labelname}%
     \setunit*{\printdelim{nametitledelim}}%
     \usebibmacro{cite:title}%
     \setunit{\printdelim{titleyeardelim}}%
     \printdate}%
    {\usebibmacro{cite:shorthand}}}



\begin{filecontents}{\jobname.bib}
@Book{Gastineau2010,
  author    = {Gastineau, Gary L.},
  title     = {The Exchange-Traded Funds Manual},
  isbn      = {978-0-470-63734-0},
  publisher = {John Wiley \& Sons},
  address   = {New York},
  year      = {2010},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}


\begin{document}
Text\footcite[Vgl.][78]{Gastineau2010}
\end{document}

Note that the ampersand & needs to be escaped to \& in the .bib file.

There is no need for the "S." in the postnote argument for the page number. biblatex can automatically add the required "S." page prefix if you load babel or polyglossia with the German language module.

I don't think it is good style to include a space at the beginning of the prenote argument (as in [~Vgl.]) if you want more space between the footnote number and the text, you should define that globally (how you'd do that may depend on your document class, which isn't shown in the question, so I won't address that here).