There are a variety of options that you can use to tailor the generator to provide more cost-effective meal plans. Just note that when you adjust any of these settings, you'll need to regenerate any current meal plans to see these changes reflected.

Generator Settings
On the website, you can go directly into the Generator Settings, and on the app, you'll find this in Preferences > Generator Settings. You'll see a "daily price limit" setting, which you can adjust to the "low" option to exclude foods that are generally more expensive.

On this same page, you'll also find a "generator focus" setting. There's an option to select "groceries" as the focus, which will let the generator know you'd like to prioritize using more of the same foods to help reduce your weekly grocery list, though note that this will come at the sacrifice of more variety in your meal plans.

Leftovers
The Premium subscription plan includes a leftovers feature that you can use to set up patterns for repeating meals throughout your weekly plans, which is another great way to reduce your needed groceries each week. On the website, you can go to Meals & Schedule > Leftovers to set this up, and you'll find this under the Preferences menu in the lower right of the app. You can see more about this here: How do I automate Leftovers or Meal Prep?

Recurring Foods
In your Meal Settings for each meal, you can set recurring foods. You can use this to set up some of your favorite budget-friendly recipes to recur often for particular meals, and then the generator will try to incorporate these options into your plans more often. Here's more info about setting up recurring foods: Using Recurring Foods to incorporate more of your preferred foods