Mary..
First know that putting a catalog together is expensive. Your first one is going to be the worst because you have no basis. Succeeding ones are built off the first.

First identify all the items you want to carry in it and break out seasonal items into groups. You can do one general catalog that has everything and then either seasonal or holiday catalogs. Some companies only recover the basic catalog each year and add new items.

If it's going to be a 4-color catalog you'll need a good photographer, artist, and copywriter. In some cases manufacture's will provide you with transparencies or color separations which can reduce your cost significantly.

Once you have your first catalog done you'll know how to allot space for each product. Cost out every square inch of the catalog and determine your cost per sq. in. Then make sure each product is paying for it's space...if not, cut it back and add something else in that will pay for itself. The last catalog I did was I think a 38-page 4 color and it ran about $70k all inclusive.
Good luck
Denny