Incentive Plan For Travel Agency Employee

We are travel agency Having 15 Employees, we have don't have any incentive as of now for our company.
But we are looking for a incentive structure. The problem is we don't have fixed margin for a booking.
So how should we go about it. How we should keep our incentive structure.
We need you guidance on the same.

Dear Gosanbi,
Travel industry is seasonal, hence you must have already identified between high volume sales quarter and the lower volume ones.
Often the selling point is the package that is offered and not how aggressive the sales team is .
Given the fact that you have already considered this , how do you differentiate between the incentives ?
I mean during the high volume months the numbers would rise on its own. Are you going to increase the percentage on sales, offered as an incentive, during the lower volume months ?
How do you differentiate between selling package for an In-demand location and some exotic one ?
You can either offer a fixed slab for incentive on selling X number of packages and recurring if there are more or less in number . You may alternatively define the percentage that you may offer as an incentive, on each package.
If you keep a fixed slab, it would need to be regulated with respect to the Holiday Season.
Looking forward to hear from you.