IMO, you should target the persons who would most likely search for a particular keyword relevant to your affiliate product. You mentioned you are discounting on PPC campaigns due to your limited budget. Its a sad thing because PPC draws in targetted traffic. It is a effective way given the proper treatment. Identify your niche and select the market you want to cater to and start from there. Research also on the keywords your desired market would most likely be looking for. You should be more focused on getting targetted traffic than just random traffic. Buying targetted link backs are also effective at getting targetted traffic. Its a matter of "matchmaking", you give your traffic what they need IMO
I started a thread on effective ways (paid and free) at this thread :
Most effective ways to get traffic to your site ;)
You may find it useful
Best of luck buddy!