In my personal opinion, problem is not with the lead generation, it’s mostly with conversion.
Suggested solution could be, build a portfolio first. What most development companies do is try to convince the Client after getting the lead, but think of a situation where the client gets to have a first hand experience with your product catalog at the time of a minor lead generation itself. The client can see how flawless your development works are and this helps in quick decision making process of the person on the other side. The conversion automatically increases day by day and you can now focus more on building new ways to enhance the development process, which in deed will increase your client number and satisfaction rate, rather than spending time a lot on grabbing the clinets.