Is there an easy way to have my whole document with a space between paragraphs rather than indentation?

Adding

\usepackage{parskip}

to the preamble of your document (the part between \documentclass{...} and \begin{document} will set the paragraphs to have no indentation and a bit of space between them.

Note that this isn't a complete solution, because there may be elements in your document that you don't want this format to apply to (footnotes, for example). A proper solution would involve (effectively) writing a new document class.

You can read a bit about how the parskip package works by looking at the comments in parskip.sty itself.

Some classes support switching to vertical space between paragraphs instead of indent paragraphs. For example all KOMA-Script classes support option parskip with several values:

\documentclass[parskip=false]{scrartcl}
\usepackage{lipsum}
\begin{document}
\tableofcontents
\section{parskip=false}
\lipsum[1-2]

\section{parskip=full}\KOMAoptions{parskip=full}\selectfont
\lipsum[1-2]

\section{parskip=full-}\KOMAoptions{parskip=full-}\selectfont
\lipsum[1-2]

\section{parskip=full+}\KOMAoptions{parskip=full+}\selectfont
\lipsum[1-2]

\section{parskip=full*}\KOMAoptions{parskip=full*}\selectfont
\lipsum[1-2]

\section{parskip=half}\KOMAoptions{parskip=half}\selectfont
\lipsum[1-2]

\section{parskip=half-}\KOMAoptions{parskip=half-}\selectfont
\lipsum[1-2]

\section{parskip=half+}\KOMAoptions{parskip=half+}\selectfont
\lipsum[1-2]

\section{parskip=half*}\KOMAoptions{parskip=half*}\selectfont
\lipsum[1-2]
\end{document}

Values full and half distinguish in the amount of space between the paragraphs. The postfixes influence the minimum amount of free horizontal space at the last line of a paragraph.

To change the amount of space between paragraphs, you want to change \parskip.

This adds an extra line between paragraphs:

\setlength{\parskip}{\baselineskip}

This removes the indent at the start of paragraphs:

\setlength{\parindent}{0pt}