If you can, get gallon cans from a cafeteria. Put concrete in them to an equal height. Set your table legs into the cans. While they are heavy to move around, they will not wobble and you can make them any height you need.
An alternative is to purchase PVC pipe larger than the table leg you wish to put into the pipe. Drill holes through the pipe on opposite sides of the pipe and slide a stove bolt through the holes and secure the nut. Drop the table leg into the pipe and it will rest on the stove bolt. It will be very sturdy and is easy to set up and remove and you can set the bolts at any height you require.