Congratulations!! Well done becoming vegan!
You don't need to eat expensive. You can buy beans, lentils, potatoes, other legumes oats for breakfast, nuts, and lots more, that contain many calories and you will easily become full (except for a variety of fruits and vegetables ). Make sure that you eat a very healthy vegan diet with lots of nutrients.
I recommend this website: www.drfuhrman.com (ignore the parts that aren't vegan)
Also this website: http://www.tcolincampbell.org/
It is important to eat nutritious and healthy food so that we live longer to help the animals and inspire other people to take care of their health too!!
This Facebook-page is very helpful to learn how to advocate veganism effective and not contra-productive: