The readings below are mostly organised according to first-year modules but those texts are worth reading regardless of whether you take the modules in question.
General texts
Mary Midgeley (2018) What is Philosophy For?
Thomas Nagel (1989) What Does It All Mean?
Greek Philosophy
Plato The Apology of Socrates
Plato Meno
Elementary logic
Graham Priest (2017) Logic: A Very Short Introduction
Political Philosophy
Adam Swift (2013) Political Philosophy
Epistemology
Jennifer Nagel (2014) Knowledge: A Very Short Introduction
Ethics
Julia Driver (2006) Ethics: The Fundamentals
Metaphysics
Alyssa Ney (2014) Introduction to Metaphysics
Modern Philosophy
Descartes Meditations
Hume Enquiry concerning Human Understanding
Methodology
David Papineau (2012) Philosophical Devices
Some Miscellaneous Suggestions
Tim Crane (2001) Elements of Mind
David E. Cooper (2002) World Philosophies: An Historical Introduction
Lorna Finlayson (2016) An Introduction to Feminism
Barry Dainton (1980) Time and Space
Samir Okasha (2002) Philosophy of Science: A Very Short Introduction
Naomi Zack (2018) Philosophy of Race: An Introduction