I would recommend PW as the most important. Then BWD and PP. The love spell / EFT book if you are going to do that. I've not used the EFT for this, but I have used it for other things in teh past and it is definitely helpful.
If I had to recommend one thing only it would be PW. I would also recommend buying any/all of the meditations. Again, PW is probably the most important. You can do it without them, but it is a bit easier to start off with the recording.
You will need the Kindle app to read them.