A lifting belt is a tool and not a form fixer. When your form is acceptable, start using a belt when you can afford one from a reputable brand (INZER/SBD/PIONEER). Don't buy a cheap dropshipped belt from amazon. Leave a comment on your preferred belt brand to help another lifter out!
There are multiple benefits to using a belt:
Reducing lower back fatigue. Therefore you can tolerate a higher squat and deadlift frequency.
Reducing the overall risk of injury by increasing tightness and positioning through proper bracing with the Valsalva maneuver.
A belt will not make your core weaker. If you are ever concerned about a weak core, just train the damn thing directly.