Games organizers frown on the idea of clan tents selling items. The games usually get a percentage of the vendor's sales. So that potentially cuts into their pockets. The only thing that could get by are items that the clan produces exclusively for it members.

What could you use the material for? Table cloths, bean-bag paper weights, mini flags, and of course a sash for yourself. You could make extra sashes for Gordon members who come "un-tartaned". This way they feel better about marching in the parade of tartans.

As for the cost of the tent, the clan itself might pay for it. Each clan has its rules for paying for these, so check with them.

Good luck!