I have heard from several Rabbanim that one of the best sources for strengthening emunah is reading parshat Ha-Mahn, which you will find listed after Shacharit in most Siddurim.
Many people don't say this at all, and those that do, probably run through it too quickly and routinely to appreciate its true messages. Parshat Ha-mahn is more than just reading a history lesson and is more than just a lesson about relying on G-d for parnassa (one's essential needs). It is mainly about emunah.
Think about it. Why didn't G-d just leave the mahn like a huge supermarket where there was so much of it that people could take a lot and store some of it for later? In the story, you see what happened to people that left over the mahn. It got wormy and melted. So every day, people had to go into the field to gather mahn for just that day. Why? To teach people their emunah. How did everyone know that the next day they wouldn't have mahn? Indeed, that's what happened to some people on Shabbat when they went and didn't find it. They thought The mahn had ended! Only when Moshe reminded them, that it was just on Shabbat that they wouldn't have mahn (which is why on Friday they took a double portion) were they re-assured. That was a temporary lack of emunah.
In short, try reading parshat ha-mahn daily. Read it with some good commentaries, perhaps, so that you can understand and better appreciate how G-d provides everything you need each day, every day. It is more than just a historical lesson of emunah. Its message is highly applicable to all of us today, as well.