The emergency fund is an amount of money kept in cash, in a safe and fully liquid place, covering between 3 and 6 months of your essential living expenses: rent or mortgage, food, utilities, transport, insurance. This money is not invested. It is not touched except in a genuine emergency. It is your shield.
If you invest all your savings and tomorrow you lose your job or face an unexpected medical expense, you would be forced to sell your investments at the worst possible moment, perhaps with the market falling. The emergency fund gives you the peace of mind to let your investments grow without touching them under any circumstances.
Where to keep it: In a remunerated bank account or an easily accessible deposit. Not in investments. The priority is that it is available immediately, not that it earns much.
Your essential spending is $1,650 per month. Your emergency fund would ideally be between $4,950 (3 months) and $9,900 (6 months). That money is not yours to invest — it is your safety net. Only when that is covered is the money you put in the market truly money you can leave untouched.