[Mashiro]

You would be wasting money and other resources (time, nerves, electricity, etc...) following the route "i was thinking of adding external gpu instead of buying a motherboard with a gpu connected to it".

That notebook is not meant for gaming at all. The CPU is absolutely garbage given how old it is and how entry class (low end) it is (also not to mention how bad mobile CPUs were back in the ages of 2nd Gen Intel i Core). Your notebook has no interface to support the necessary performance and computing power of an external GPU. You don't have USB-C and you don't have Thunderbolt. No external GPU for you. Also again the CPU would be an instant bottleneck where everything would still run very bad while you GPU would be "chilling in the corner" because it has to wait for the CPU.