We are installing a 12' gazebo from the local home store. It has a covered roof, metal supports, and pull-back screening to keep the bugs out.
We took out a small flower bed in the back yard and plan to install the gazebo over it. My concern is what base I should have for this project? I can't have grass cause the shade will kill it anyway... my older MIL needs a somewhat firm base so she won't fall... I don't really want to install patio stones (144 @ $2 ea)... I thought about paver base and tamping it down, but don't think it will hold well, but maybe if I put something like a tarp over it... pouring a concrete base is too much... give me some ideas?

 

Well, you've pretty much ruled out all the GOOD ideas... doesn't leave us with much.

Since you mentioned an elderly MIL that probably rules out any sort of outdoor carpet type of rug or "tarp". A sheet of 45 MIL EPDM would cost you about $1.50 sq ft. and then you have to deal with the perimeter.

Landscaping fabric and a couple inches of wood chips come to mind. Just can't picture wanting to walk on that or have chairs sitting on it. Concrete or pavers are your best choice.

 

just went to the store and thinking of paver base, tamping, 5 x 7 outdoor carpet by the entrance and wood chips around the rest. Gazebo is really 9' x 12'. I may have to attach large feet to the chairs.

 

To keep the gazebo standing during high winds you need to stabilize the steel corners. What I did is use planters on either side of the corners. You can fill with sand, pebbles or stone chips. Put potted plants on top as a decorative accent. My 10 x 12 gazebo has withstood 4 years of all season weather without moving an inch. And I live in Buffalo, NY.

 

So far we have no picture of what your even trying to install.
Install a metal base in direct contact on grade it will rust out in a year.
A tarp would be useless.