I always developed complicated PHP scripts that did little to no sales. Now, I'm trying to find something more simple, yet with average/high demand, could you give me some suggestions? Thanks in advance.
Consider making a mass emailer script of some sort. I constantly see people asking how they can email their lists. Make a script where one can enter their email list, push the button and the script will do the rest (will keep sending emails either one by one or in batches depending on the amount a user chooses from a drop down menu).
List your php scripts in codecanyon.net to get a review of your script by experts and lot of users will find your script. You can also find what is trending scripts and users interests.
Never got accepted there... And they don't even give you a straight answer of what is wrong with your script.
I could do that, still, It would require people interested, otherwise I would (once more) waste my time.
I am kind of similar position. I see is not just me. I guess its because we dig into our loved code and forget the marketing/demand part. I was thinking in just getting someone with no code knowledge at all to exchange ideas.