Blaze your trail
If you want to enhance your knowledge on formulas, take a look at the following Trailhead modules:
Using formula fields: https://trailhead.salesforce.com/content/learn/modules/point_click_business_logic/formula_fields
Advanced formulas: https://trailhead.salesforce.com/en/content/learn/modules/advanced_formulas
Evaluating report data with formulas: https://trailhead.salesforce.com/en/content/learn/projects/rd-summary-formulas
Improving data quality for a recruiting app: https://trailhead.salesforce.com/en/content/learn/projects/improve-data-quality-for-a-recruiting-app
Improving data quality for your sales and support teams: https://trailhead.salesforce.com/en/content/learn/projects/improve-data-quality-for-a-cleaning-supply-app
