You can make the sides any length (30, 32, 36 inch) and width probably 32" is best. Use two 4" strap hinges and tie a string from one side to the other on the bottom to ensure it doesn't slide out under pressure.
Also, here are the plans I drew up if you want to make it the same size (that way you don't have to use the ellipse formula to know where to put the screws for the focal points) That took a lot of time for me to figure out the shape of the table as there are not any websites for building an elliptical poker table. Also, buildyourownpokertables.com has a lot of useful step by step info.