The only notebooks for which these officially exist are the newer Alienware systems.
A few of the XPS models with Thunderbolt 3 ports may work with some eGPUs - but even that's trial and error and unsupported. There are very few Inspiron systems with Thunderbolt ports -- and these are very new models (no more than a year or so old) -- as with the XPS, it's going to be trial and error to find one that works, as there is no official support.
With a Celeron CPU, even if you could use an external GPU (which you can't, for the reasons ejn63 described), the CPU would become a major bottleneck to the GPU. And since you didn't specify the exact Inspiron model, I can't be certain about this, but I'm going to guess that a Celeron-based system doesn't have a lot of RAM installed and probably has a low maximum memory capacity as well, which would become another bottleneck for most games. If you want to play modern games properly, you'll need a better system overall.