In general...

They will pay you for reasonable costs for things you needed during your trip. I don't think they pay you for things you bought after you got home.

They pay you for the depreciated value of anything lost or ruined. In other words, you paid $50 for some slacks last year, and have worn them 20 or 30 times. The depreciated value of those slacks might be, now, $10. That's what you get. Supposedly, you could go to a thrift shop and find slacks that have about 20 or 30 times worth of wear and replace what you had for $10.

If anything is missing, you would have to be able to somehow prove that you owned it in the first place. You can't suddenly "remember" you packed an expensive Armani suit or new Coach handbag.

I'm no expert on this, and I invite correction from those who know better. This is just what I have picked up in my years of travel. Some say to take photos of your bag as you pack. I don't do that, but now I'm thinking I should. With digital photography, a bunch of photos don't cost me anything.