If a spell says it has a gold requirement but doesn't say it consumes the gold, do you still need the gold? I have been told that regardless if the spell has a gold requirement, that your focus can't replace the gold as a component. Is this true?
I assume that by "gold requirement" you mean a material component with a specific cost.
I have been told that regardless if the spell has a gold requirement, that your focus cant replace the gold as a component. Is this true?
Yes, that is true. PHB states:
A character can use a component pouch or a spellcasting focus ... in place of the components specified for a spell. But if a cost is indicated for a component, a character must have that specific component before he or she can cast the spell.
It also says:
If a spell states that a material component is consumed by the spell, the caster must provide this component for each casting of the spell.
Therefore, if the spell doesn't state that the component is consumed, then the same component can be reused, so you wouldn't need to buy a new one.