What city / town are you close to? Trying to determine your zone.

I take your attic is vented to the outside and the floor of your attic is insulated.

Can you tell me what type of insulation you have now?

Zone is Oakland, CA.

Yes, attic is vented to the outside and the crawl space also has insulation.

I have fiberglass insulation now.

Air sealing the ceiling plane is the important part. Then lots of insulation. Lots of ventilation. Radiant barrier on the rafters will help.

Oakland has relatively moderate weather as the OP knows. It's neither very hot in the summer nor very cold in the winter. I think the minimum insulation standard here is R30, about 10 inches of fiberglass batts, as an example. Having a bit more is fine but there's a fall off in the cost/benefit relationship as you add more so to say "lots of insulation" isn't necessarily usefl. .

The OP hasn't said what kind of structure he's in but there are a lot of older homes in Oakland. Air leakage may be a greater problem than insulation. It's another thing to consider. Short of the expensive task of replacing single pane windows (which are very common), easy tasks for a DIY to start with in the air leakage department are to seal plumbing and electrical openings in walls and to replace worn or inadequate weatherstripping around external doors and also windows.

I'm not an expert, just been researching some myself. But, my basic understanding is that radiant barriers do help some, but not a drastic amount. I've read about 5-10% savings if the house is otherwise well insulated. And that insulation is more important. I've used an attic fan before in my previous house, and it helped. My current house has ridge vent and I think it probably superior.