I think there are a lot of configurations to take care of for configuring search in your application.
To start with you should first have ATG search installed with your core atg software.
Then use cim to configure your database to configure search related scripts in your database.
Once you are done with the DB, then use the following modules to your build.
I have also included the CRS related modules but you can exclude them if you want
For commerce instance
For CA instance
BIZUI,PubPortlet,DafEar.Admin,B2CCommerce.Versioned,DCS.Versioned,DCS-UI,Store.EStore.Versioned,DAF.Search.Versioned, DAF.Search.Routing,SearchAdmin.AdminUI,DCS.Search.Versioned,Store.Search,Store.Search.Index,DCS-UI.Search,DCS.Search.CustomCatalogs.Versioned, DAF.Search.Base.QueryConsole,Store.EStore.International,Store.EStore.International.Search,Store.EStore.International.Search.Index,DafEar
Also it would be good if you go through the installing and configuring atg search documentation