I have just completed a shower project and would like to know if I should seal the grout lines.Should I seal the tiles as well (ceramic) and what type of sealer shoulld I use ??

Whose grout did you use?
Always a good idea to seal the grout. Makes regular maintenance a little easier.

The tiles do not need to be sealed, only the grout joints.

As for sealers, it depends on what's available in your area.
Do you know what brands are available in your region?

I used Mapei grout, I got lowes and home depot here,not sure what they carry

I prefer the Dupont sealers from Lowe's over Home Depots Tile Lab products.
Dupont has a specific grout sealer that is water based.