You don't mention your surname, which muddles the issue, nor do you say where you live now or from whence known lineage springs. Some would say if your surname is not a clan name or known, accepted associated family, you have no clan and therefore no tartan. Others would say that's irrelevant,
wear what you like, but at least know what it is and who those folk were, and do it respectfully. Others would say wear something connected to what is known

William the Lion was descended from David I and Duncan, son of Crinan and Bethoc, so the line runs to MacAlpin. This is also part of the heritage of Juliana. Therefore, one could say he is honoring this line by wearing MacAlpin,
Or Dunbar, or Dunbar district. Duncan would be as appropriate, though many
say Duncan ancient is not real, though Leslie of Wardis would work. John Duncan of Sketraw, a member here, is head of the clan Duncan society, moving toward re-establishing the clan. You could offer allegiance and beg membership.

There is an old Perthshire district tartan that would reference Crinan and Bethoc as well. If you live in the U.S., most states have tartans, there are military tartans to honor your service there, Union and Confederate, Scottish heritage, Caledonia, Warrior, etc.

No matter what you choose, somebody will tell you you're wrong, so be forewarned. If you have what takes to wear the kilt, you probably have what it takes to handle the guff.