Either loose fill (typically fiberglass or cellulose), batt insulation (usually fiberglass), or spray foam will work well.
Batt insulation is easier to install yourself; if possible, install the new insulation perpendicular to the attic floor joists to reduce heat loss through the joists. Loose fill insulations are typically installed with a blower machine. For a DIY project this can be rented from most hardware stores or you can hire a contractor to complete the work. Spray foam will need to be installed by a trained professional.