Im slightly disadvantaged as to having no culinary background or food truck friends or relatives to bounce ideas or strategies off of
If you have industrial areas around your area hit those up for sure. Figure out when/where lunch breaks are going to take place and be there. It's going to probably take a little leg work and talking to people.
Burgers, burritos and dogs tend to do okay.
Burritos are fast, cheap and easy to throw together. They have a high profit ratio vs food cost.
Learn to make your re fried beans from scratch. Crock pots are good for this and you can generally leave them unattended while they're cooking.
Dry beans are cheap.
As far as recipes you don't need to be a chef nowadays. Youtube/the internet are cookbooks.
Make sure your food isn't bland either. Learn how to season the right way. Not enough to overpower everything but just enough to give it some flavor.
Have a visible sign out front for people to inform you if they have any food allergies. I've personally witnessed someone go into anaphylactic shock due to a food allergy. Check your ingredients on EVERYTHING if inquired. Even down to the seasonings.
I guess one of the most important questions to ask would be what is your truck equipped with for heating and preparing food on the go?
I assume a fridge/freezer. Do you have a grill, oven, fryers? Are they all up and in working order?