If a socialist movement seized power in the country next to yours, would it be better to move there or stay where you're at and try to build your own, benefitting from the momentum?

It depends on your personal situation but en general, I'd say helping to spread the revolution in your own country would be more beneficial. A revolution can not succeed in the long run to establish Socialism when it's isolated in one country and also the momentum of a successful revolution in a neighboring country can be incredibly powerful. Just look at the revolutionary shockwave that the bolshevik revolution sent through Europe.