Actually it doesn't have to be first time. I've been doing it like this, at least for costumes:
Disable texture saving and remove the equipment.
Go inside/outside house.
Enable texture saving and wear the equipment.
Usually I got the texture after doing that. If not, I just repeat the step again until I got it. I did that to refresh my modded textures too, everytime I made changes on my modded textures.
Since Resorep just grabs every texture coming onto the screen whilst it's in capture mode, I find it helps to reduce the number of files to look through to find what you want.
Firstly make sure your Resorep saving folders for DXT1, DXT5 & the other one that nobody cares about are empty and the tick box for capturing textures is unchecked.
What you can do is put the armor that you want to get the texture files for on your character and then exit to the character selection screen.
Pick one of your other other characters to display on the main screen (don't enter the game).
Alt-TAB to Resorep and check the box to start gathering textures.
Alt-TAB back to BDO and select your character wearing the armor you want to display on the main screen (don't enter the game).
Alt-TAB back to Resorep and uncheck the box again.
This way you've gathered a fairly small amount of textures and the one(s) you want will be easier to spot.