Everyone should have a couple people that they are able to have conversations about God with. I'm not trying to say you should only hang out with Christians but I am saying have friends that are Christians that can support you as you walk with God. That way you are going through similar issues and can help each others grow closer to God. It's not the same with friends who aren't Christian no matter how good of a person they are they can't understand some of your problems because they don't try to follow God's rules or struggle hearing His voice. Christian friends are a great support system to have and it's easier to keep a strong relationship with God when you're surrounded by people who are trying to do the same thing. You are accountability partners for each other and help keep each other on God's path. I have a lot of non Christian friends and they still have helped me through some hard times but the Christian friends helped remind me where God comes in to the situation. It's not a bad thing to have friends that aren't Christian but I also highly encourage you to have some friends that are Christian that you trust enough to talk with them about more serious and personal issues.