You can still believe in God if you like even though you do not believe In Islam. Ask the Christians and the Jews. You can still be spiritual without believing in any religion. Spirituality is a personal path and has nothing to do with religion. 

I can tell you about my own path but what works for me may not work for you. You have to find your own path. You can read about my spiritual thoughts here: 

But if that rout is not for you, go to the sites of other religions and study them. Buddha has very good teachings. I think many ex-Muslims can find solace in Buddhism. There are some unproven teachings, such as reincarnation in Buddhism too. You do not have to blindly accept everything. Just pick and choose what to you seem logical and right and leave the rest. This is the essence of Buddha’s teachings. He said doubt everything, find your own light.

Leaving Islam also does not mean you leave the belief in God. If that is what you are comfortable with, you can continue to believe in God. If you like praying to God, make your own prayers and just talk to him. Religions in general are unsubstantiated beliefs, but if that does not bother you, Christianity is a good religion. Better than Christianity is Zoroastrianism, but that is a religion mostly Iranians are reverting to.

What is important is that there are many ways to reach God. The best ones are those that teach love and make you feel closer to your fellow human beings. The only way we humans can experience God is through love. A religion is true to the extent that it teaches love and is false to the extent that it instills hate. This makes Islam the falsest religion and the most dangerous one.