Off topic-ish, but maybe someone here would know... I have a 2013 macbook pro. It's still great for coding but recently I got into Blender, and now I understand why you might want an external GPU. Is that a possibility for such an old laptop? I couldn't find any definitive information on how to go about buying one, and setting it up.
More critically, at least in 2013, the docks you needed cost thousands of dollars—and made more sense to just get a separate desktop PC. I don't know if the situation has changed since then—there are more eGPUs out there but it's all for Thunderbolt 3. Thunderbolt 2 is more niche and thus may be more expensive.
The rule of thumb is: use an external monitor and the highest resolution possible. Sending control commands one way consumes much less bandwidth if you don't need to send whole images back down the link, and the high resolution and quality is to make the GPU the bottleneck, not the TB2 link.
I was able to get a ThunderBolt 2 Mac to work with a Razor Core + Vega 56 combo, but YMMV. Away from computer so don’t remember exact year for my MBP, circa 2015 maybe?