From my research the consensus is that true Ceylon cinnamon does not have the problem with coumarin that Cassia cinnamon has. Of course Cassia cinnamon is more common and much cheaper than Ceylon cinnamon.You need to be careful with cinnamon. You can actually OD on it.
I use elderberry for immune support and that is about it. I know there are a lot of other herbs you can use too. I don't get too into that though. I have started growing micro greens. Eating a balanced diet is really a better way to go. Limit sweets and fats, lots of veggies and fruits, whole grains.