An open gate is a harbinger of promising opportunities in the near future.
Dreaming of a closed gate is an obstacle dream. However, the obstacles can be overcome if you work hard at it.
To judge exactly what obstacles you face, look to other symbols in the dream.
A locked gate implies obstacles that are practically impassible, unless in the dream you also find ways to go over it, under it, or around it.
In the latter case, success is practically guaranteed.