The internet is full of free IELTS material. Most of it is garbage. Here's what actually moves the needle.
1. The British Council's free practice test
Free, official, and the questions are similar in style to the real test. Use it as a baseline. Take the free practice test ?
2. Cambridge IELTS 17 (paid, but worth it)
The 4 most recent official practice tests. Every one is an actual retired exam. If you only buy one book, buy this. Cambridge IELTS 17 ?
3. PassPilot's free diagnostic
You get a full band score plus a personalised study plan in under 60 seconds. Better than any quiz you can find online. Create your free account ?
4. BBC Learning English (intermediate level)
Daily listening practice that matches IELTS speed. Free, audio included. BBC Learning English ?
5. The IELTS Liz YouTube channel
Best free video lessons for writing and speaking strategies. Liz explains the rubric in a way no textbook does. IELTS Liz on YouTube ?