Could you make, like $300 bucks off web games?
There's companies that make millions of dollars from web games... so yes... but these companies also spend millions of dollars making and marketing their games though...
Aiming for $300 is kinda incompatible with wanting to run a professional business. $300 pays for, like, one day of professional labor. A real business plan would be based around spending over $300 a day for quite some time to produce a polished product, which you can then use to try and recoup those costs.
If you're aiming to earn $300, then you're probably going to be producing a non-polished product with zero marketing spend that won't attract any paying customers.