what are some good nutritious snacks?

I am new to this. I have never dieted. This is so inspiring. In two days I have started to make conscientious choices in the foods I am eating. I never drink water. Iced tea and sodas. I quit sodas two days ago. I drank 6 glasses of water today and I can't believe how this program makes me feel. I don't eat a very balanced diet. I never have. I seldom eat fruit. I do eat veggies at dinner. Any ideas on good snacks that are full of nutrition. I ate 900 calories today and this thing told me I am not eating enough calories that being undernourished by the foods I chose can keep me from losing the weight I want to lose. Im 51 and starting gaining weight around the gut. I am not very active. I'm Walking. Am planning to paddle board (SUP) with my husband, but have only done it once. Great core exercise. And No I never exercise. I got on the treadmill tonight and will start with baby steps. Only did 1 1/2 miles. I am at my highest weight 155. I'm 5' 7" and I want to lose 10 lbs to start by my grandsons first birthday. I have 30 days.