Priscilla, The sealer you use is dependent upon the type of tiles you have. There are several good quality sealers available to you at the big box stores. No one sealer is better then another. Just read the backs to be sure what ever you choose is for the type of tiles you are sealing. Make sure the tile and grout is clean and dry. Do the sealer in a spot that you can hide or not normally seen to make sure it does not darken the grout or tile. Once you choose your sealer, be sure to use enough of it until it does not soak in any more. At that point dry the tile off with soft absorbent towel and your good to go!
Aqua mix, Fila, Oceancare