Scott's site is an obvious starting point for great Arsenal stats.
The current king of statistics sites is Fbref.
Statsbomb is a great general stats site with strong analysis and useful tools like radars.
Understat is a good starting point for all things xG.
Whoscored is a place to find the basics. Passing percentages, shots, tackles, touches. All the stuff we used to consider "stats." Now you need a PhD in mathematics to be a football supporter obviously.
Transfermarkt has information on player contracts and transfer market valuations.
Arseblog isn't just a great blog. His site has fantastic tactics articles and statistical breakdowns.