If you want a sealer then believe it or not walmart sells a floor wax name HOLLOWAY HOUSE. It will protect your floor and you can even wash your floor to get wax off if you want. Them reapply after washing. Great floor wax and the only place you could get it was at Rennigers flea market in Mr Dora FL.
If it has lost its luster and you want to improve the look try Rejuvenate. It can be purchased at Home Depot. It helps with the grout too.