Hi JayFCF
I started as an affiliate in Feb this year, but do have a background in online marketing so maybe had a bit of a head start. I was having trouble getting many natural sales (non-PPC) until I read Stu Foster's Nichefather. Although I knew the theory, it really helped drive home the importance of finding a niche that has both little competition and a fair amount of traffic.
See the NicheFather here
One of the most important features of the Nichefather is Stu's template, which although basic, has all the right elements for high search engine ranking. Study it and then create your own version based on it.
The other article that really helped me look at affiliate marketing in the long term was
This Blog
I've moved on to becoming a full time affiliate since then and can see why it was worth all those months of working until 2 or 3am. I tried many avenues and eventually started to find some that worked well. Now I just focus on those and put out a few feelers every now and then to find my next niche.
Good luck with it. It's hard work but the rewards are high. I'm sitting in my local pub (my second office) writing this so can't be all bad!