What reading do I have to do?

The short answer here is: you need to do enough reading to achieve mastery over your subject's objectives and to address your assignments to the standard you're aiming for.

For subject objectives

Focus on the week's objectives. Find answers to those objectives in your reading material. This means you do not read every word of your articles. Instead, you will quickly search through the article to see if it covers the area you're interested in; if it's relevant, then you'll spend time looking through it but only to find the answer to your question.

Remember, you will not be assessed on your recollection of the content of articles; instead, you will be assessed on your mastery of your subject's learning objectives. This means you do not have to read every single item on your reading list but you do need to read what is relevant to the study objective.

For assignments

Reading widely is encouraged in your study and will certainly help you write a more informed assignment, although some tasks will not require this (see How many references are enough?). You may not, however, have sufficient time to undertake a wider review of your literature. Be strategic, then, in how much reading you undertake. If you're happy with a credit, for example, then perhaps you'll confine your reading to the bare minimum.

Look at the guidance in Language and Learning Online on approaching a long reading list