I am new to apex, and want to learn from scratch. What could be the best practice for that?

@Hitesh Sharma  

Apex Basics → Variables/Conditions/Loops → List/Set/Map → sObjects → SOQL/SOSL → DML → Classes/Methods → Constructors → Triggers → Governor Limits & Bulkification → Test Classes → Async Apex → Integrations.

Practice every topic with small programs in Developer Console/VS Code.

Start with Salesforce's Apex Basics & Database module, then move to Apex Triggers and Apex Testing. Apex Basics & Database – Trailhead Apex Developer Guide