I am hoping that someone has an answer to this one!

My Scot connections are (on my mother's side) Douglas, and (from my father) MacKillop. I know that many (though certainly not all) members here would tell me to wear whatever tartan I please. I would greatly prefer, though, to wear the ones that I would normally wear had I been born in Scotland and raised in a traditional fashion, or at least those that I can confidently say are a part of my history. This would limit me to my own very rare (and so extremely costly) family tartan, as pictured as my avatar. I rather like it, but cost is a major factor and it will be quite a few years before I can invest in a custom-made kilt in that tartan. There are various MacDonald/MacDonnell tartans that may be acceptable, but I remain uncertain as to which ones.
Though again some here may disagree, I would not have any problems with wearing the Douglas tartan to honour my grandmother. To do so, though, I would want to formally make the request from someone who can officially grant such permissions, but there is no Chief of Clan Douglas, so am at a loss of who I should be contacting.
If there is anyone here who can enlighten me, I would be very grateful. Also, if there are any here who can clear up matters regarding which MacDonald tartans are plausible choices, I'd love to hear from you regarding that as well.
As a side note, cost is not the only factor that would make me hesitate to go with the MacKillop tartan any time soon...I look absolutely terrible in red!