Is it advisable to use robo-advisors for investments for a regular investment amount of $200? ?

You can invest in a Regular Savings Plan through fund platforms or banks, or a Global Portfolio via Financial Advisors either digitally through Robos (like Stashaway) or traditionally via Independent FAs like myself. :)

I recommend investing with a strategy in mind, and with an understanding of asset allocation that will adapt throughout your investment journey, do remember to rebalance your holdings as well to maintain your risk exposure.