While I have not dealt specifically with CESM, I can infer some things about it. By definition, CESM is an earth systems model, not an exoplanet model. You may be able to adapt some of the parameters to other planets, but it becomes too difficult for just one person to do (because of FORTRAN). There are models for other places, such as GCMs for Mars, but they are difficult to run and not necessarily accurate. Clusters are needed due to memory limitations, and how long they run for.

2) Also i just came across a GCM that claims to be user friendly called EDgcm. I know nothing about it, but it looks worth digging into.

3) There's an intriguing app called "GCM" I've honestly never messed around with it, but it could be worth a shot.

4) Here's an energy balance climate model that can be executed in excel.

If you're determined to use a GCM, I think you could probably get CESM working using either the aquaplanet or dry dynamical core setups. Depending on how simple you set it up, you could likely run it just on a standard PC. Another option you have is MITgcm, which can also be configured to run very bare-bones simulations that don't require much computational power.

If you have a university near you, I would consider seeing if there are any climate modeling groups, and reach out to see if there are any grad students willing to lend a little support. I know grad students who spend usually the first semester of their phd trying to get a simulation going.