1. There is a tread in debate section that will have more responses on this topic than this thread will populate that is dedicated to the question "does god exist." I recommend taking a look there for anyone considering this question.
2. Before looking into an exact answer, consider what you want or need to develop an answer. There are many who will claim there is evidence for god and those who say there is not evidence for god. Some use philosophy while others look at mathmatics. Some point to miracles or scientific laws. Oral tradition can be looked at while others decide to ignore oral tradition.
I would suggest being open minded to some evidences that we otherwise might not consider. Looking at the reasonings behind such evidences. For example, if I dont think mathmatics is involved in determining god's existence, there is no harm in seeing why bob thinks it does.
3. If we look at evolution. We have creatures who have some trait that is same or similar to a previous generation. This leads back to different species converging to a single genetic link. The evolution of many species looks like a tree branching off from an origional source. This is the same for religion and faith, diversifying as man adapted and migrated.
This is part to how we see so many similarities in religions and cultures. From dragons to flood stories. For example, when settlers visited americas, some natives identifed adam and eve story to be similar if not same as their own creation stories. These things develop through oral tradition that over time changes due to variations in human wants.
Id say this develops in same way religious groups split today or 500 years ago or 1000 years ago. Different opinions vs different attitudes. I compare it often to a group of hebrews worshipping a golden calf. Unpleased with x, therefore I say/do y.
4. There is no evidence to suggest everything religious is based on filling a gap. Many aspects is not based on a therefore b. Instead we see more instances where a supernatural being is accredited with being able to do a and therefore is believed to be doing a. For example, lightning being caused by or associated with god of thunder because god of thunder is capable. Not necessarily, i see lightning therefore a god is doing it.
I am sure some may believe everything occurs as a direct cause, but even this may stem more from a god always having a direct influence. Ex: jupiter controls the weather therefore we appease him to maintain a good healthy weather forecast. If forecast is bad, then jupiter changed it because a,b,c. Here the guess work is more along the line of how do we fit into the overall equation.