I've found that certain symbols get you in different places. The first one I tried was the swastika, strangely enough this portal key got me into a place I refer to as valhallah. Another one I tried was the three triagles symbol, this one brought me into an open grey room with straight grids along the walls much like the holodeck in startrek TNG.
I haven't tought about making my own portal/gateway keys yet. You might have to come up with one that is unique for yourself only. Or I think you might run the risk into running into a place that already exists.
I'm still trying out various symbols.
My strategy is to follow the most common and universal symbols starting from the ancient and working my way to the modern.

Eventually I want to explore higher dimensional shapes because I think they will offer more interesting possibilities.

I think it could be interesting to try out new and unique symbols and to try them out with other people to then compare our findings.
Good luck out there.