Hi Deanna, how's Eric? Depending upon your location, r-30 for mid america and r-38 for northern states. R-38 won't cost that much more. What do you have in their now? Maybe some of that can be overlaid or use it for overlay. If you are moving around, adding too, or replacing insulation, make sure you fill all air gaps around lights, junction boxes, vent fans, etc. with caulk or foam sealant. Check along the wall cavities where there may be leakage and damming.
Easy for a diyer just messing with and breathing itchy fiberglass and crawling around in a hot/cold attic and trying to avoid stepping through is a pain. Have a helper so one can measure and install and one stay down to cut and hand stuff in and out without climbing in and out. Leave an air gap into all soffit areas where the roof truss meet the walls. The fiberglass fits between the joists and sticks up when you have r-30 or r-38. Just for the heck of it get a bag or two of blow in type insulation and throw it in by hand to fill in the joist spaces. Staple a piece of batt to your attic entry door.