I think 15 days should be good enough to score you 7 - 7.5 (but all depends on the intensity of your practice).
- Practice 5-6 hours every day, rather than 12 hours two days before the test. That's my advice.
RE: the resources, I highly recommend that you use official material and books written by experts rather than online random resources. Why? Because This approach will not only prepare you with the right material but more importantly train your non-english brain in a consistent manner. Consistency is key to success in IELTS. Your mind doesn't function randomly and can't focus on different sources, you have to be consistent in your practice. You don't want to jump between different types of material(s). Stick with 2-3 books with their own attached audio, and you will be fine.
If you go to the thread I shared some official material that I came across here:
http://www.canadavisa.com/canada-im...s-books-tests-download-links-included.501746/
The following book list is a MUST:
A. Cambridge (Official) IELTS 11 General Training (2016). Student’s Book With Answers (Ebook & Audio CD) ** Top Selling**
B. The official Cambridge Guide For IELTS 2014 Edition 10 (For Academic & General Training)
The above books do have tests included, but they're more or less for learning purposes.
Therefore, after you're done with each book, I highly recommend that you devote 3 full hours + 15 minutes, sit in a quiet area to do the full practice test (including speaking). This will give you the full test experience.
1. IDP IELTS Full Test (General Training Module)
2. IELTS Canada Full Test (General Training Module)
3. IELTS British Council Samples Test (General Training Module)